My Macbook Air (2017) has slowed down considerably and I don't use any additional apps which would cause it. Currently it's on Big Sur OS. Should I upgrade to new Monterey or downgrade to previous versions. I have heard that newer OS are not compatible with old hardware and that might be causing slowness.

OpenCore can allow you to go to Monterey but no guarantee of speed i would suggest to reinstall as a recovery partition after doing backup of all data as TimeMachine + local manual backup

My device is eligible for Monterey update

Then go for it

I think a simple format and reinstall everything from scratch should offer a performance improvement.

@loud-glass-33663 IDK if that improves performance on a mac, on windows I definitely agree, I’ve seen clear differences whenever I’ve done a clean install, not so much with my mac. In the last 6 months I did clean installs on a mac 2 times, since I wanted to downgrade a couple of times and after sometime, upgraded to the latest (these were direct upgrades, not clean) but I’ve never noticed any performance difference on my mac.

@thousands-morning-63911 Definitely helps on Windows but does on the Mac as well (in my experience). When I got my MBP16, I had restored it from Timemachine from my previous MBP2012 (which I was using for 5 years without a clean install). Finally after a year, took time off to do an install from scratch and immediately noticed things starting up quicker and being more responsive. The other (more conclusive example) would be my wife's old MBA -- which is pushing 8 years now. It was unusable. Super sluggish and took forever for anything to happen. I did a clean format + install and now I can atleast use it for basic stuff like web browsing and emails and journaling. So crud does build up over time + if you are restoring often, the backwards compatibility of some things tends to make things slower.

the issue isnt just a clean install. Big Sur and Monterey have added new frameworks that make old systems sluggish and slow so no way around that. thats one reason why old iphones and ipads are not getting iOS16 too

Also get your macbook cleaned, sometimes the fans are filled with dust can cause it to slow down