I think it's a mixture of flaw and incompetence. The corruption is certainly a thing, especially with smaller orgs, but I honestly don't think that's really an issue with the UFC.
Incompetence is 100% a big issue. Many judges are simply not following the scoring criteria. There are judges who are still to this day scoring simple control time above effective striking/grappling. That's probably the most notable thing as of late.
But MMA judging is flawed in that it's quite subjective. It's incredibly difficult to have people agree on whether or not 5 good strikes should be scored better or worse than 1 great strike. People always like to scream about damage, but even that is incredibly subjective. Just because a strike cuts a fighter, that doesn't mean that it did more damage than the strikes landed by the other guy. Some fighters show wear and tear more obviously than others. Some guys cut, bruise, and swell easily, whereas others might need to take a prolonged beating before showing much at all. It's not uncommon for the strikes that don't look like they did much to be the ones that actually hurt the fighters the most. Five minutes is a long period of time to judge, especially when using the 10-point must system. It's not like we're using some criteria here where you get a set number of points for successfully performing a certain action.