To me, sanity is not conforming to old idiosyncrasies. I have had multiple people yell at me in person when I bring up clipboard. This is probably the single most embarrasing thing I have ever seen in Unix or Unix-like systems. We can't even get copy pasting right.

Sane defaults mean a single clipboard. If I copy something, it replaces the contents of the single clipboard. If you want to keep track of all the old things you copied, that's fine but all the ways of pasting should always paste the last thing you copied. If we can't agree on something simple as this, we can't agree on defaults (and should give up on computing).