For me, I gave up trying to find rigged and animated 3D chars online, I grab T-pose chars, rig and animate them myself (I hate A pose, I don't have the skills to rig that properly yet).
The reason is not the scarcity, it's simply because I find it impossible for the needs of a specific game, you will always end up needing very custom and specific animations if you want to do a relatively long game. You see, sometimes I need a hit animation in a specific part of the body without having to turn the mesh into ragdoll for a simple hit (no 3D artist would predict all these needs, unless it's a dedicated assignment), sometimes I want chars with rigs in each finger, sometimes I don't (because of performance in population rendering), so that's why I found it easier to learn how to rig them myself in blender.
So finally answering your question, the most valuable resource to me are 3D collections (of anything, interestingly I can easily find 2D collections). Collections of shoes for instance, or collections of hair, or food. The reason is consistency, I can easily find those separately from multiple artists online but if there's little to no consistency among them it may make the game art look like a frankenstein, multiple different arts glued together in the same game.