The same thing has been seen with KDE 4 and 5, Gnome 3, and how long LXQT has taken. Users hate experience regressions passionately, and will actively hate projects that depreciate or replace their workflows, sometimes for years, and sometimes forever.
At the time, I was quite unhappy at Canonical for making their OS so difficult for me to use. I felt that I was being totally left behind, with a machine that was just old enough that it wasn't worth it to them to support it.
1 or 2 years later, I tried a newer release of Ubuntu on that machine. Unity was definitely more stable than before, but it was still frustratingly slow, and had sprouted the weird, unwanted amazon search feature. I continued to be disappointed that the default install of Ubuntu had become so needlessly graphics-intensive, and haven't played with it since.
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One other gripe with Unity -- I really didn't like how it thought that applications were more important than windows. It was difficult to switch between 2 or more windows of the same applications on the same desktop. The icon on the taskbar just showed a tiny arrow for each window. You had to hover over it before it would show buttons (icons? previews?) of each window that you could select. Alt+Tab was the same. You could only rotate between applications, but if you held it down for a moment, it would show the windows of that applications, and there was some way to pick between those on the keyboard.
I really didn't like that. I would often have 2 or more terminals open, or text editors, or file browsers, and I would want to switch to the one that I had least-recently used, and I would have to do this whole dance of pulling up the application, waiting to see the individual windows, and finally picking the one I wanted. The 2-3 seconds that took were very frustrating, since I knew that I had used to be able to hit Alt+Tab a couple of times to go directly to the window I wanted.
I have the same frustration every time I have to use an apple computer. It bugged me enough that I read through the keyboard shortcuts settings and learned about Cmd+Tilde, which helps, but is still very frustrating. I want a window! Why does it take two different kinds of keyboard shortcuts to get to the window I want!
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Between those two troubles, I am happy to have avoided using Unity.
I'm getting old enough to belive you.
For me however while I can believe it I really really cannot understand it: it broke my workflow in a number of ways by default and unlike Gnome 3, Unity was next to impossible to reconfigure to something I could use productively.
It is actually somewhat of a learning experience for me to see something I almost despised be missed by a number of people.
I think two easy conclusions should be "different strokes for different folks" and "make your software configurable".
I was using Cinnamon (first on Linux Mint and then on Manjaro) for a few months before the release of Gnome 3.32. I've switched to Gnome 3.32 and it feels much more responsive than Cinnamon. In particular cycling windows and doing anything while a notification is being displayed.
I really wish Cinnamon didn't stutter as much. It's the right amount of "desktop" I need.
The constant UI flux is the worst part about using Linux.
I've moved on from Mint, but the fact that the MATE dev community took the tried and true paradigms learned from Gnome 2 and made kept them alive in spirit won me over. I installed Ubuntu MATE to a box just the other day.
Not to imply that it isn't valuable on high end machines (it is), but I personally really like Gnome 3 these days once I got used to it's way of doing things.
A constant window manager is actually one of the strong points of linux. Lot of people still use twm.
Both responses on their own are perfectly reasonable, but it's understandable if users get a bit frustrated.
To give another example, one upgrade my Xmodmap stopped working, and I had to stop everything to learn how xkb worked. If there is some package I could install to just have Xmodmap work again, that'd be great, but I wasn't able to figure it out at the time.
Out of the box its not very configurable, but install compiz settings manager and its very good.
sudo apt install ubuntu-unity-desktop