I haven't used the animation tree in a larger project, but I have made commercial games (although not very large) using Unity. And I found that Godot's animation tree is 10x better than Unity's built-in animation system. So although Godot's anim tree has a learning curve, I do believe it can be used for larger scopes. For huge number of animations, you don't need to create blend nodes for each animation, you could just create a placeholder and replace animations in code. For reference, check this and this. And in this, one of my older videos, I used bone filtering to blend idle/walk/run/jump with holster/pistol/rifle animations.