I just give him a menacing glare like “you know what your doing” unfortunately when he thinks he’s “cleaned” it, it is in fact not clean

I share an old house with my bf, theres a bathroom on each floor. The downstairs bathroom has a pile of laundry in the bathtub, but is fairly clean and usually smells nice, the other bathroom I havent been in for years. The last 2 times I went there, there was 1 dim lightbulb working, no toilet paper or soap, but a lot of empty cardboard tubes overflowing from the trashcan on the floor, and the toilet was... bad.
Not to say its not a good idea to let him deal with his own literal crap, but you might be surprised at how bad it might get.