I'm glad you have found the performance of 2.3.3 to be better!
The Arduino CLI developers definitely did some optimization work that was shipped in Arduino IDE 2.3.3 through the update of its Arduino CLI dependency from 0.35.3 to 1.0.4. However, the optimization discussed in this topic is not in Arduino IDE 2.3.3. So beta testing is still welcome. We didn't receive much testing on the proposed optimization and I think this has made the developers nervous to move forward with it. So the lack of testers is one of the reasons why it didn't end up going into Arduino IDE 2.3.3.
Although it is unfortunate that we missed it in Arduino IDE 2.3.3, the fact that it is still to come is actually good news in a way because it means there is potentially even more improvement beyond what you already saw coming in a future version of Arduino IDE.