Severe Perf Issues and Crashes make the game unplayable

That sounds like the auto-save that happens every cycle, and is a natural progression of a colony as time goes on. If you don't care about your colony summary reports and those pretty graphs, you can use https://steamcommunity.com/sharedfiles/filedetails/?id=1867707267 to speed up those save times. You can also reduce the frequency of autosaves (I personally use 5 cycles)

Actually, I found that *something* had my memory pegged at 99%, which was what was impacting the game.  I am not sure what did it, but the game is running fine now.   I will open a new issue if I find that ONI was the cause of the memory leak.