The people who really drive ms office adoption are the ones who use it all day every day. They can't imagine a world without Excel, and (at the time) the cluttered formatting of the office controls were a power user's best friend.

When the Ribbon UI came around in office, it faced a ton of push back due to moving so many things around and hiding so many common operations, but the file format translation issues between office and alternatives kept people in the MS cage, I think.

Nowadays many users grew up with the ribbon, so it doesn't seem so painful.

I don't think its the ribbon.

I grew up pre-ribbon. I did not like the ribbon. MS Office 97 still had a way better UI than anything open/libre office did.

If i had to rank, i would say

Old pre-ribbon ms office > ms office with ribbon > [a large gap] open/libre office.