Windows 7 is great and Windows 10 is fine. Windows Vista and 8 were the worst of the culprits in terms of merging a mobility OS into a desktop one. The reason Windows's PC's tend to slow down is because Windows does an inept job of cleaning up after itself (temp and update files) and the self management of its convoluted registry hive.
My daily machine is a 2017 - 27" iMac and I wouldn't trade it for the anything. I have another 27" iMac from 2009 (11 years old) still turns on and still work fine. (never had a reinstall done on it)
This post wasn't meant to debate the two, as a Network Admin I support both and a bit of Linux as well.