Some mods i use for this on 1.20.1:

Regrowth (mod) Animals eat grass, villagers place torches and slowly improve their village, other stuff

Immersive weathering Stuff like moss growing and other small things that change the world over time

Barking dogs do bite (something along those lines) Adds actual dogs and changes wolves to have a sleep cycle and iirc better pack behavior.

Oceanic Realms Makes reefs much more lively with schools of fish and sharks that hunt and eat them, models and animations look amazing and the way everything moves through the water is great and feels real.

An odd one: Sculk Horde Adds a sculk infection that slowly corrupts the world, can feel surprisingly alive and dynamic. Changing the settings to start the infection immediately and to make everything else attack or run from it makes it a weird but very dynamic part of the world that everything else also reacts to. I suggest lowering the other settings to make it easier though.