I'll add one other bit to this excellent post: in some ways, good technique gets worse and worse looking as the situation gets more chaotic. To an extent, this is the same as #2, but can apply even when the other fighter isn't making them look bad - it's just the nature of chaotic combat going all-out, as often happens in MMA, especially at upper levels.I will argue that there is no one currently in the UFC solely on the basis of their physical attributes. All of them are very, very skilled. Even those who aren't world class still have much more overall skill than most hobbyist black belts (and honestly a high percentage of instructors who run their own schools).
If you see a UFC fighter who seems to have bad technique, there are a few possibilities.
1) He or she is using their technique in a way that you don't recognize because you don't have the right background.
2) The other fighter is making them look bad by virtue of even better technique or ringmanship.
3) They might actually have a bad habit on one area or another, but are compensating for it with superior technique elsewhere.
15-20 years ago you had some fighters who got in the UFC based just on physical attributes. Today the skill range is from very good to absolutely unreal.