All versions of Windows after Windows 7 are just UTTER GARBAGE (Except Windows 8.1). i'm still holding out on Windows 7, and i managed to hack the updates to get ESU until next January.
but as long as i am still using this toshiba laptop, it's sticking to Windows 7.
Windows 10 and 11 will have shit performance on ET because the OS is made to run modern programs, ET was made for Windows NT4/98/ME/2000/XP so obviously it won't run that well on the current Windows versions so you'd probably be better off with ET Legacy.
if you are dedicated with vanilla et, you can still get better performance by installing it into "C:\Games\WolfET" instead of the default directories, no "Run as administrator" necessary! also make sure your ET is patched to 2.60b with the Masterlist patch. you can get a pre-patched 2.60b ET here: https://www.splashdamage.com/games/wolfenstein-enemy-territory/
and the masterlist patch here:
but there isn't much you can do with improving vanilla performance, it's just the way it is.