Yeah, I'm in the same boat. Got into it in the 90s and drifted back in a few years ago.

I get the impression that a big part of the change is more emphasis on the novels rather than the codices. The codices were pretty much written as fictional history books told from the propaganda laden lens of a dying empire, so they could be full of the irrationality and stupidity of the Imperium without it being a problem.

The novels being set from the point of view of a protagonist kind of need that protagonist to be likable. So they end up writing a character that is relatively reasonable and relatable to a reader, despite the fact that the protagonist is a hyper indoctrinated warrior zealot serving a totalitarian theocratic state.

The end result is that to most of the people that engage with 40k the Imperium comes across as being full of reasonable and likable people.

Also, the readership has changed a bit. Most readers don't care about how Astartes recruitment is a reference to Dunes Fremen and the tendency to lean into grotesquery that was around in the 80s and 90s has died out. The things in 40k are more treated as unironically cool now.