MCprep 3.6 will remove the Cycles optimizer for the following reasons:
Hasn't caught up with latest Cycles developments
Algorithm is extremely buggy at times; there's been cases of it setting max bounces to values like 80. Ironically, I don't even use the optimizer (despite making it) for this very reason, and opt to manually optimize my scene
Better tools exist for automatic optimization; the Super Image Denoiser devs at Pidgeon Tools have SFR, a Cycles optimizer that actually profiles the scene, making it far better then what we have.
While the intent of the MCprep optimizer was to have something tuned specifically for Minecraft animation, I feel that over time, that became "how do we optimize a scene while not profiling, due to the average user's hardware?"
(mostly copied from https://github.com/Moo-Ack-Productions/MCprep/issues/514#issuecomment-1868565367)
MCprep 3.6 will remove the Cycles optimizer for the following reasons: