Couldn't you simply use macOS without the iCloud features? Which features require iCloud to work?

You can but there's just not much point anymore.

I don't remember all the specifics but every time there was a new macos I could cross most of the new features off. Nope this one requires iCloud or an apple ID. Nope this one only works with other macs or iPhones. Stuff like that. The Mac didn't use to be a walled garden. You can still go outside of their ecosystem (unlike on iOS) but then there's not much point. You're putting a square peg in a round hole.

Now, Apple isn't the only one doing this. Microsoft is making it ever harder to use windows without a Microsoft account. That's why I'm gravitating more and more to foss OSes. But there are new problems now, like with Firefox on Linux I constantly get captcha'd. M365 (work) blocks random features or keeps signing me out. My bank complains my system is not 'trusted'. Euh what about trusting your actual customers instead of a mega corp? I don't want my data locked in or monitored by a commercial party.