First, This is only a problem if you have very diverse needs and most users' needs aren't.

We need to run a browser, a terminal, a file manager, maybe some media apps, and a text editor if you don't do that in the terminal. This is not like a vim config of an industry veteran, it shouldn't require tweaking from the OS. Just get out of the way.

I can tweak the number of workspaces or the colours temperature for day and night. These are matters of personal preferences. But the way to launch apps, connect to wifi, or display a clock should just be ergonomic.

Second, tweaks don't solve this problem.

There's a handful of talented tweakers and power users. They will use Sway or whatever anyway. Everyone else when confronted with lots of knobs ends up with something worse than a competent designer could have provided by default.

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).

That's not true. People want an "intuitive" UI, meaning familiar. While there are some outliers, most people find Windows and OS X UI conventions familiar. Sticking to these conventions as "sane defaults" pleases most users.

You can always install packages if you got exotic needs. But Ubuntu being the most popular desktop distro, I'd say they managed to find a popular mix.