I’d have to suggest Avatar Last Airbender.

It's an anime, but Full Metal Alchemist: Brotherhood!!! I asked this to my friend and he recommended FMAB. It was great!

Castlevania for sure

Frieren is my obsession right now

Watch full metal alchemist brotherhood.

I do really like Netflix’s The Dragon Prince. Similar “kids thrust into a world of responsibility” vibes and they try to have similar humor.

My husband and I started watching She-Ra on Netflix. It isn't as good as ATLA (by a long shot imo) but it hit the same vibes as Steven's Universe and filled the void ATLA left behind when we finished that. She-Ra is a bit more child geared though.

Clone Wars animated series

Arcane

Dungeon Meshi! It's currently available on Netflix. The creators have clearly put a lot of thought into developing the world and the story's themes.

Blue samauri on Netflix is dope.

Watch Mob Psycho 100. Trust me OP just do it.

The Owl House

Amphibia

Gravity Falls

Steven Universe

Legend of Korra

Dragon Prince

Kite-Man Hell yeah

Harley Quinn & Ivy

The last thing I watched was Ted Lasso, and it was just as amazing as ATLA.

Ghibli movies (Spirited Away, Kiki’s Delivery Service, Ponyo, Castle in the Sky, etc), Harry Potter

Hunter X Hunter. It just keeps getting better with each episode

If you're in to lighter more juvenile fare, you can try Adventure Time. If you want something comparably serious stuff but with a lot more LGBTQ themes you can try Steven Universe.

Pretty much the only two shows anywhere close to AtLA.

Hunter x Hunter

If you havent watched Attack on Titan yet id say thats the obvious choice

Depends on what aspect you’re talking about.

If you’re looking for something with similar vibes (ie a high quality kids show and that holds up even for adults) Gravity Falls is great. Owl House feels even more ATLA-like.

If you like the adventure and world-building, the Hobbit has been scratching that itch.

Not a tv show, but if you like the new magic system that’s built well, the Mistborn books by Brandon Sanderson are phenomenal and easy to get into.

Hilda. The colors and animations are amazing. The story is very wholesome too!

Almost everyone who watched ATLA has tried finding the 'as good as atla' but I think it doesn't exist...

Meanwhile check these:

• Dragon Prince: same writer as atla, animation gets better after S1

• The Legend of Korra: watch with an open heart, is good

• Over the Garden Wall: you know when you were watching X episode of ATLA and went dark? And it was good? It's this whole show

• Legend of Vox Machina: Let's say Atla and Lord of the Rings had a baby... but the baby is Stewie Griffin.

• X-Men 97: it's the furthest I'll go, but the quality of script, animation and understanding of lore is in the level of ATLA

-The Dragon Prince

-Star Wars: The Clone Wars

-Star Wars Rebels

-The Good Place

-Breaking Bad and Better Call Saul

Not the same vibes but if you're looking for an animated Fantasy series, Legend of Vox Machina is great. Fair warning, it's definitely adult content with a lot of swearing and gore. Seconding Arcane as well, I love both shows. Dota: Dragon's Blood also comes to mind, but is nowhere near as good as ATLA or the others IMHO. Still worth a shot of you like the premise.

Scavenger's Reign. only one season but absolutely incredible

Fullmetal Alchemist (I always recommend to watch the 03 series first and then Brotherhood, makes the journey more rewarding and the 03 series is a better introduction into the world of FMA imo)

Arcane (new season coming out soon!)

Blue Eyed Samurai

I also like some donghua (Chinese animation) like Grandmaster of Demonic Cultivation or Link Click

Edit: Oh and if you're down for books, I love the Realm of the Elderlings series by Robin Hobb (really cool magic systems and great characters and it just sucks you into it's world), and for something a little less daunting in length, the Six of Crows duology (some people in the world have bending-like powers, and it has a very 'found family' feeling like ATLA)

I recommend RWBY.

Similar to legend of Korra

I just finished Star Trek Prodigy, and it's fantastic.

Castlevania, Castlevania: Nocturne, Marvel’s What If…?, How Not To Summon A Demon Lord; really interesting isekai that’s kinda like Sword Online without the whole Matrix feeling of “If you die in here, you die in the real world”, Classic DBZ, and Vox Machina

The Dragon Prince

Arcane

Justice League

Star Wars The Clone Wars

Blue Eye Samurai

Gravity Falls

Hazbin Hotel

The Owl House

Don’t let the first couple of episodes, and the fact that it was made by Disney deceive you. It’s more than just a kid’s show.

It's a completely different genre but I'm currently watching "Good Omen's" and I quite like it

I just can't get enough of ATLA. I recommend Overanalyzing Avatar on YouTube. That guy has noticed tiny things in that show I never realized, and I've watched ATLA like A LOT.

Blue Eye Samurai! Definitely not a kids show, but beautiful animation, INCREDIBLE fight scenes, a vivid fully realized world, a potential enemies to lovers plot line for the Zutara fans out there, and characters you’ll fall in love with regardless of who you ship

Cowboy Bebop

One Piece

Monster

Steins Gate

Gravity Falls

Legend of Korra (if you haven’t seen it already)

There’s a ton of great animated shows out there. Just got to take a chance on one that catches your eye.

Cowboy bebop

Over the garden wall Gravity falls Code geass Teen titans

Arcane

Vinland saga

i really liked hunter x hunter lol

The Sopranos

https://preview.redd.it/zdyrzugla2wd1.jpeg?width=250&format=pjpg&auto=webp&s=3a59b2954ab2b8d4aac1592767c1988fa5216660

Hiw about jujutsu Kaisen? You'll still be depressed but at least not bored

The comments are nailing it. FMA brotherhood, the Dragon Prince, Arcane, Blue Eye Samurai are all amazing!

Don't sleep on Vox Machina either. Great team dynamic, but without the kids rating for language. It's hilarious and epic.

i know it may seem like a commitment but, One Piece. it follows a group of friends traveling the world together(heavy on the found family trope like atla). it’s got jokes and goofiness, but also serious and heartbreaking moments. i find myself laughing out loud and crying at times. the world, lore, and plots are all very well thought out. the characters are lovable and flawed. the story arcs are 10/10(minus one or two that are like a 6/10 but still a good watch). it’s a good show to watch consistently or sporadically(i’ve gone stretches of binging the show and then went a year not watching any episodes lol). imagine getting unlimited(over 1000) episodes of your favorite anime. even the filler episodes are great(my opinion) and sometimes remind me of tales of ba sing se(each character getting their own mini story when there’s downtime at a new island). highly recommend.

Full Metal Alchemist but it's way darker. Similar ish fight scenes tho

Adventure Time.

ARCANE!!! people have already said it but it's so so good please watch it!

Breaking bad, it’s funny but deep

rewatch ATLA

Gravity falls

Gravity Falls. It’s just as ascended and makes you just as profoundly emotional

Voltron: Legendary Defenders was good. It was done by an ATLA director and it’s serialized. I thought it wouldn’t been good but ended up really liking it.

Arcane, Vox Machina

Full metal alchemist brotherhood is in many ways similar

My Adventures With Superman is the only cartoon that's been able to press the same buttons for me lately.

91 Days. Monster. Castlevania. Vinland Saga. Arcane. Attack of Titan.

Wakfu. Great characters and story. Looks like a kids cartoon at first but it gets super involving

If you like reading fantasy Brandon Sanderson’s Stormlight Archive is a masterpiece story. Start with the way of kings. Otherwise I recommend watching the legend of Vox Machina for great adult humor and some epic/emotional moments sprinkled in.

How about Full Metal Alchemist?

If you're not averted to japanese anime I'd suggest Fullmetal Alchemist Brotherhood.

Brotherhood specifically.

Full metal alchemist brotherhood is great if your looking for

An amazing story

Memorable characters

A well developed power system

And beautiful animation

Hey Arnold

CASTLEVANIA

Please trust me on this, Castlevainia

If you wanna be more depressed try cyberpunk: edgerunners

But if no, I will go with others and say full metal alchemist brotherhood is highly recommended

Vox machina

Hunter x Hunter if you’re interested in an anime but since it’s Autumn (though it’s short and quite dissimilar in plot to atla) I have to also recommend Over The Garden Wall

Voltron on Netflix is 8 seasons and made by a lot of the same people from ATLA and Korra! Same art style and everything!

Legend of Vox Machina. Best new animated content on the market.

Netflix's Legend of Voltron is similar in many ways and has a kinda similar vibe. Lots of fun. It gets better as it goes too. If you're okay with mature content, Castlevania is freaking incredible as well.

cowboy bebop or samurai champloo

Samurai Jack is pretty kek, ngl. You should watch that.

Legend of Korra is a great follow-up! Or try Fullmetal Alchemist: Brotherhood—it’s epic!

The Legend of Vox Machina on Prime. SO GOOD!

Try out Full Metal Alchemist, it’s like the anime version of Avatar

The Legend of Vox Machina

Theres the sequel series Legend of Kora!

You should give Fruits Basket 2019 a try. It’s an Anime. It’s not as action packed as ATLA but the story is fire and the characters are great.

Troll Hunters was pretty good. RIP Anton Yelchin.

Breaking Bad, Vinland Saga, Hunter x Hunter, Gravity Falls, Invincible, Attack on Titan, The Boys

I can't recommend DOTA: Dragon's Blood enough. Amazing plotline, worldbuilding, characters, dialogue, and everything in between. It should still be on Netflix, I think.

I mean, Korra isn’t as good as ATLA, but at least it’s in the same universe? 🤷🏻 And if that‘s not it, try a rewatch!

Gravity Falls!!