I definitely agree that WIndows 11 SUCKS when flight simming in FSX!
I have a fairly powerful gaming PC. Ryzen 7, 3700X with 64Gb RAM, GTX1060Ti video card and massive paging file for extra umph.
I also have a Dell Inspiron with an Intel i7 with 32Gb of RAM, GT1030 and large paging file, which is not qualified for Windows 11.
I installed Windows 11 on the gaming box. FSX performed like I was on a 486 with 8Mbs of Ram and a video incorporated on the MB.
I followed all of M$ help instructions to make WIndows 11 perform better. I kept running out of system memory and CTD.
I reverted back to Windows 10 on the gaming box and installed Orbx high end scenery and maxed out my video slides in FSX.
I am running between 50 and 100+ FPS consistently.
I am not going to be switching to Windows 11 until absolutely forced to do so.