Try Firefox maybe? Safari and Firefox work perfectly on my 13 year old MacBook… I don’t know what’s wrong with your machine.
Edit: you can’t put Windows 11 on a 13 year old machine, that’s a straight-up lie. Mind you, not because the hardware is broken or unsupported, but because Microsoft simply refuses to allow it.
All you've said is that it's fine because you can run Windows 10 on old hardware, but somehow being able to run a fully supported version of macOS isn't good enough.