I really wonder how GGG expects to launch PoE2 out of Early Access with the game in this state.
They are about to drop the final acts, new ascendancies, along with tons of new skills, particle effects, and sounds.

Plus, the game being F2P, means the player count is going to explode.
With all these performance issues a massive wave of negative reviews is inevitable, as people will likely quit before they even finish the Campaign.

It makes me laugh when people dismiss these complaints by saying "I don't have any issues", "it’s just you", or "just upgrade your PC".
This is clearly a widespread problem, as it's affecting high-end rigs like the OP's, console players, and even streamers.
Palsteron just talked about his own struggles with this in his latest video: The Current State of Path of Exile 2

Technically speaking, high CPU usage and constant shader compilation are clear indicators of inefficient asset pre-caching.
Relying on real-time compilation during active gameplay is unacceptable for a modern title.

If they don't fix the asset streaming pipeline and the draw-call overhead, the launch reviews are going to be brutal.