The fact that MLG allowed moves that some perceive as Customs may have contributed to the renewed crusade against fun.
That's the thing. There are people out there who are sour about custom specials for the fact that some of them are too powerful, and yet those very moves can also be very beneficial to some of the lower-ranked fighters in the game.
Without Wizard's Dropkick and Dark Fists, Ganondorf's recovery is just very awful as a whole.
Similarly, Charizard's horizontal recovery is improved with Dragon Rush, as it can't be stopped prematurely, and it doesn't hurt Charizard either.
On the other hand, some of the high-ranking fighters do get some good benefits out of their custom specials as well. In Rosalina's case, Shooting Star Bit makes it easier for her to put pressure on slower fighters who lack reflectors (such as Ganondorf and Robin), while Guardian Luma helps her deal with fighters who lack projectile attacks better (such as Meta Knight and Captain Falcon).
I would like to correct that, by standard opinion, without Wizard's Dropkick and Dark Fists, Ganondorf (noun, not adjective) is just very awful as a whole. As has been his entire archetype for the history of Smash, because the entire design point of the mighty glacier archetype fails in games like Smash where mobility and survival is so central to a character's ability to perform well (happens in other games, too, of course).
You could take Needle Storm and give it to Ganondorf and I doubt he'd jump past mid tier. But where the difference in view and perception comes into play, between players who actually have views besides "This isn't fun to me," is that some (such as myself) are more than willing to give a bad character a good move and let them average out to okay, and even give a good character a good move in exchange, than have a bad character be permanently bad by design. Others are willing to accept the arbitrarily default way that the cookie crumbles, so to speak.
I think another issue is set up time. There are only 10 slots for a ton more combinations. (I am not doing that math.) I know some events set 10 that players could choose from... but it can be argued that standardizing them like that defeats the point of customs... but not doing so mean's someone who uses an unorthodox set needs to take the team to leave the smash menue, go to customs, set it up, then play... then may need to do it again if they switch charecters... then if someone wants the set up that is deleted later they need to go back for it.
There are several solutions to that issue.
For small tournaments, setup time shouldn't be an issue. There are two approaches to this. On one hand, the most pro-customs of scenarios is that everyone uses a unique moveset (there are 81 combinations per non-DLC character, though by virtually all opinions not all of these are even "worth consideration"), and in a worst-case logistics consideration (proper from a planning stance but unrealistic), you end up with a massive time sink. However, in this case, the time sink is even across contestants, few, if any, players should feel reasonably slighted, as they themselves were given their share of setup time.
On the other hand, there's the approach that customs "aren't widespread and thus create inconvenience." In my absolutely biased viewpoint, this defeats itself. If customs create an issue, but people don't use customs, the issue cannot manifest at a larger scale, and thus provides no cause for banning. In a related train of thought, is me taking half a minute to make a set (provided the ruleset allows thus instead of forcing the Moveset Project sets, addressed below) any worse than my opponent pondering between Sheik or Diddy for the same amount of time? Until I see a tournament get held up, and that hold up be solely and completely attributable to the implementation of custom moves, it's impossible for me (as a logistics expert) to use that as a justification against customs.
Lastly, the idea of the moveset project limiting "secret techniques" or however you want to term the idea of a pocket strat built around customs not in the top ten voted sets. It's an unfortunate side effect of tournament scale, but ultimately, "if you don't vote, you can't complain." But you
can, if your life circumstance permits, just go to a tournament that will allow you to show your pocket strat and maybe win with it.