I mourn the loss of the Unity Desktop which was virtually perfect OOTB. It had a great management of the screen space, especially on laptops, it was pretty, and it worked. I wouldn't even change the desktop background.
That's what Ubuntu gives me, that's why I've used it since replacing Debian testing in 2006.
3,500 servers on 6 contents can't be wrong either, with all our software distributed as debs, it just works.
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).
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.
My customized GUI really needs to be consistent across my machines, and Unity makes this impossible to guarantee and automate. Just give me an .rc file, text-based configuration is my favorite part of Linux.
It's also particularly dangerous, since it leads to the "my way or the highway" GNOME mindset, which, in the extreme cases, entirely removes features without the option to enable them back, because... customization is bad.
When we ask for customization, we're not saying that the default setup can't be usable, or that hours of tweaking should be required before getting started. We're saying that when there is a feature that doesn't behave as desired, we would like the option to modify it. "It works this way and that's final" is already well served by other operating systems, why do you feel Ubuntu should copy this?
Ads in the OS are awful. If this has to exist, it needs to be off by default with clear, easy-to-find knobs for removing the spyware. Of course, like everything advertising-related, the incentives are to do the opposite.
In this case I personally find it in consequential for myself; I know what I'm doing and can easily remove Ubuntu's garbage. But it is an ugly trend and reduces my trust in their judgement.