I didn't hate Unity, but it had a bug (for me, and clearly a bunch of others based on the launchpad bug traffic for the bug I filed) that persisted for the entire time Canonical owned it, that meant I couldn't use it.
I could repeat it very easily, just start the application using alt+f2 and use the keyboard to launch it (terminal, chrome, whatever). When triggered a window wouldn't be accessible over alt-tab. Was running, couldn't alt-tab to it. As someone that uses the keyboard a lot for navigation, it was a show-stopper. I have to be able to alt-tab between windows.
Eventually filed in 2012, https://bugs.launchpad.net/ubuntu/+source/unity/+bug/951929 "Fix Released" but you know, still people reporting it later on in 16.04
In fact, even now, the number of "confirmed" bugs with long life on them on Launchpad is particularly disturbing, considering how many of them are fairly fundamentally impacting.
Like, say, https://bugs.launchpad.net/unity/+bug/1126221. Filed 2013 by an at-the-time Canonical employee, confirmed in 14.xx and then 16.xx. If you had multiple displays, put a window on one and then disabled it, windows on the other screen get essentially stuck, can't be alt+tab'd to or anything.
Or https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1619563, hey I know, let's have two actions be on alt+tab. Switch windows, and close window! What could go wrong...
or https://bugs.launchpad.net/ubuntu/+source/unity/+bug/49579, reported 2006, still reported 16 years later. If you have menus like the Application open, the timed screen lock won't kick in.
Over and over and over, what could have been a really good desktop experience was crippled by stubbornly ignoring the bugs filed against it (at least, I assume ignoring because the number of times engineers would actually comment on the tickets seemed to be few and far between). Canonical repeatedly shot themselves in the foot by not nailing the basics: the environment has to work.