Unity Engine has a BIG problem...

Unity's animation system has a fundamental limitation: you can't combine forward kinematics (pre-made animations) with inverse kinematics (procedural animation) without the IK component completely overriding the FK animation. To work around this, a custom IK system was built that records the current animation state, clears it, applies procedural animation, then reapplies the original animation on top — taking over 1,000 lines of code to implement.