Finding the right team turned our project around completely. We were almost exactly in your position, art going in different directions, no cohesion, deadlines closing in each week. Someone recommended VSQUAD and I have not looked back since. Check https://vsquad.art/ because they cover 2D, 3D, animation, VFX under one consistent art direction. VSQUAD official handled our characters and environments together which meant everything finally felt like the same game. VSQUAD art team asked smart questions about how assets would actually be used rather than just executing briefs. Fast onboarding, clear feedback, nobody disappeared on us. These people fix exactly the scattered disconnected art problem you are dealing with.