Then we have the desktop environments. KDE isn't too bad, and there are some lightweight alternatives that a quasi-usable. But the former star of the Linux desktop environments, GNOME, has pretty much destroyed itself with its GNOME 3 effort. This is one of the most stunning failures ever seen when developing software. The user experience has been ruined in a way that many thought would not be possible. Yet it has happened.
See, this illustrates a big problem. I guess it's a problem with human nature, I'm not sure exactly, but it's a big problem somewhere.
You point out a big problem (and I agree, Gnome3 is a big problem; it sucks. The user experience is awful, just as you say). Then you even mention a solution: KDE. KDE isn't perfect, but it isn't too bad, just like you say. Personally, I like it, at least better than anything else I've ever used. I wish they hadn't wasted so much effort on that "semantic desktop" crap with Nepomuk etc., but otherwise it works well and lets me configure it to my heart's delight. It's reasonably fast on my older hardware and does everything I need to do. I constantly read people complaining about some mis-feature or missing feature in Gnome3, and that thing is always not a problem in KDE, either because it's easily configurable (without having to download some extension) or just isn't architected that way.
But for some reason, no one wants to switch to KDE. They just gripe about Gnome3. And many of the larger distros keep pushing Gnome3 for some odd reason (Fedora and RHEL are the most notable examples, but Debian pushes it now too). It's utterly baffling. I thought Linux was supposed to be all about giving users choice and being hacker-friendly. Gnome3 is the opposite of that; it's made with the same philosophy behind the MacOSX UI. Heck, I think even Macs are more configurable than Gnome3.
and even ads have been injected into the browsing experience!
Now you'll have to provide a citation for that one. I'm always using whatever the latest FF version in the Mint repos is, and I haven't seen any ads. And it's a lot faster and more memory-efficient than Chromium, which I've also spent plenty of time with. I'm no fan of the new UI, but the only time I really see that is when I click on the configuration button, which isn't often.