^That.
I can find no basis whatsoever that suggests it is actually "a lot of mentors" (like others in this thread said) that are doing horribly.
It's always "this one mentor did something bad, omg the mentor system is horrible and should only include those 10 people that have purple numbers on FF****",
completely ignoring the hundreds of times the mentors in their other duties were just normally doing their job or even going out of their way to help.
Because why would you go to the forums to say "today I had 3 nice mentors in my Dun Scaith run, today a mentor explained to me how the mechanics of Sophia work, today...etc."?

It's a mixture of unfair expectations (many people think mentors are some kind of uber players that should be better than the average player, but they don't know that mentoring is SPECIFICALLY linked to the newbie system, and a mentor needs to be good enough to help a newbie and answer newbie questions, NOT give an endgame static advice on how to be even better, or be able to single-handedly carry a lvl 60 party through content - because that is. not. their. job).

And yeah sure, there is the occasional bad egg, but that's ALSO something most people don't realize - they can report bad mentor behaviour and the mentor will get their mentor status removed (or, if the behaviour goes against the general ToS, will get a ban for going against the rules that are in place for ALL players).