At least on the latest Sequoia, there has been no hard requirement for an online account. They nudge you towards it, but you can decline and continue. As far as I can remember, macOS has never required an online account to set up a Mac.

You might need it for the App Store if anything, but even then... You don't need the app store for installing software. Mac is at its peak currently, though the new glass UI stuff is a little over the top for me. I miss the old simpler UI. I'm sure I'll get used to it eventually.