Kagi has a great browser, proton has mail and calendars (I mean everything has calendars, there isn’t really much lock in there), maps are (location dependent) very fungible.
The OS and documents are trickier as I’ve never used either but I did only say 70%. The thing I would find hardest would be converting sign in with google accounts
If the average person was so inclined, they could probably degoogle themselves 70% in one day, 90% in a month, and 98% in a year with very little cognitive load