Ranting about bad UIs reminds me a bit of ranting about tabloids. They are obviously bad, and nobody reads them if asked, but that does not change the fact that they are very popular.
(Please don't use bad UIs as a template if you start fresh, minimalistic is OK)
When I go to any page on the site, I get a blank page with an alien in the middle. Quite some time later, the content actually loads. If I tap a link and then go back, it goes through this all over again - and then it doesn't go back to the same scroll position but some arbitrary place.
Finally I found a menu option that let me get the desktop Reddit site. I kept trying Chrome's "Request desktop site" but it didn't work. Turned out I had to use a setting in the Reddit mobile site's own menu for this.
The desktop site is a huge improvement, but with major flaws of its own. The font sizing on mobile is fairly ridiculous - huge page titles and minuscule comment/etc. links - but at least the pages load fast and it behaves like a normal website.
What in the world are they thinking with this new mobile site? If they only fixed up the font sizing in the desktop site it would be perfectly usable on mobile - and much better than their mobile version.
Some places like Craigslist choose to maintain their rougher UI, since a slick UI will scare off some users.
I'm not a user and I don't think that I have strong feelings about their service but if forced to visit their page I'm confused most of the time.
A bad UI that can't be excused by success ist just a plain, bad UI.
While Facebook is now completely unusable on my phone, and Reddit is very close (an example of too-much-JS-gone-wrong), going on Twitter is a blast of minty fresh air at my fingertips.
But Twitter's UI is barely usable. It's not possible to search my past tweets, or someone else's past tweets, for one example.
That alone turns twitter from being a useful tool to share information into being a trivial app to share ephemeral nonsense.