- Play for a very long time staying and building around the spawning point.
Mobs regularly despawn even if they interacted with each other.
Mobs and animals stop spawning, mobs cap is reached. Observed large amounts of Llamas - see details why it happens. Really really it spoils the survival game.
While playing survival for a long time, from time to time I get a situation when no more animals or mobs appear around my home (it's initial spawing point). I think I found the cause of the issue: The mobs spawning cap is reached by leftover Llamas after their trader is killed by some other mob. For what is worse, the killing mob also does not despawn over time, killing more and more traders, and causing that point is overwhelmed by Llamas. After some searching around the base, I have found 2 of such points (see the screenshot of one of such points). And 3rd point was in the cave below the base (where I first discovered this). In all 3 places killing mob was a zombie. Each spot has 16-30 Llamas. These for sure were trader Llamas (all covered with carpet, some dropped the lead). I do not know how many places like that I have below in the huge caves system at my spawning point, but I still hear Llama sounds all around, so I think a few more are there for sure since the mobs spawning cap was reached.
I think mobs and trader's Llamas should not be marked as "interacted with Player" when they fight each other, so they can correctly despawn instead of gathering into the "Trader Llama" packs like that.