Atla is pretty long and if you didnt start watching it as a kid it could be pretty hard to get over the start of it. It starts off very slice-of-life-ish with some of the more mature themes sprinkled in between, and becomes much more dense later on. It’s also a story about a bunch of kids (who grow and learn to cope or deal with their issues later on) which isnt the easiest to identify with unless you started watching it at a young age.