A lot of people say BJJ defense has just improved to a level where guard is useless. Personally, I think it's more so that high level guard is a lost art in MMA. Mostly because It's much easier to learn a few ways to wrestle back up while defending responsibly than it is to develop a high level guard.
I don't think charles losing a few times from guard is evidence that guard work is a flawed approach in MMA. Fighters lose while forcing their wrestling all the damn time, yet nobody holds that against wrestling lol. I think guard has fallen out of favor for a couple reasons:
- it's easier to learn how to wrestle up defensively than it is it to develop a high level guard
- MMA judging, wrong or not, seems to favor the guy on top when scoring.
Also, in regards to your comment about it being better to invest your energy in getting off the mats, charles has used his guard to threaten both Dariush and Islam enough to create space to get back to his feet. Those are two of the highest level grapplers in the sport, and charles got up from under them with guard work.