I've been somewhat following the whole ordeal with Hero, and it definitely feels like it was all a knee-jerk reaction from some of the more vocal/hardcore branches of the Smash community. Though, at this point, it seems some of the pro actors in the competitive scene are also lending support towards a Hero ban, so, this isn't something that is likely to be set aside anytime soon. I also don't get the feeling that people are doing this for clout, particularly, but people really seem to be perturbed by this character's factor of RNG.
Alternatively, characters like Mr. Game & Watch with his JUDGE ability, or Peach with her propensity for pulling Stitchface Turnips or Bob-Ombs, didn't really catch any flak for being 'too random' or dependant on RNG to fight. In Hero's case, the same factors come into play, mostly in regards to his tendency to occasional pull off a critical hit. That can be a little ridiculous, especially at the worst moments, but by that same token, it speaks similarly to if you lose a stock to a Lv. 9 hammer swing. It's a dumb way to get KO'd, but, that's really all it is.
The main point here, really, is just.. the spells. Hero can do a lot of spells, which, when you factor in the language barrier between competitors, adds another layer of frustration to the whole thing. But, forcing someone to adhere to the local language doesn't really assist in this issue, either, because we can't really expect someone in Japan, or someone in Mexico, or someone in the US to learn multiple languages in order to make sure their character is on a more level playing field. That's not all that feasible on its own. Ideally, like I mentioned earlier, a better way to handle this would be to rely on imagery. Someone outside of the US may not know what the word "FIRE" in English means, but they sure as hell could recognize what the image of fire means. Stick an animatic over Hero's head as he scrolls through the spells, and that's likely a much better way to handle that.
But, of course, the other big part is some of the spells like Whack, Thwack, or Hocus Pocus. While Wh/Thw could be attributed to just, you know, another 'G&W Judge' attack -- stupid way to die, but still a way to die nonetheless -- Hocus Pocus being able to grant the user invisibility, inVINCIbility, or a super mushroom at any given point is even more RNG than the already-present RNG mechanic, and you can't really plan for that. Unfortunately, the nature of Hocus Pocus is kind of the biggest issue with the character, I think.
However, you also have to factor in how often HP shows up to begin with, as well as how often you could actually GET any of these bonuses, versus how often you may just use a normal spell, or actually hurt yourself, and in the heat of a competitive match, it doesn't really seem beneficial to try and spam HP for the chance that you won't hurt yourself, but also the smaller chance that you'll get the one thing that could clinch you a single KO. That, I think... is largely why I personally feel like a ban of the character is somewhat unfounded.
The only thing out of all of that, that I consider a reasonable justification for a ban, would be the issue with the spells' language barrier. Find a way to correct that, and I think there's no real reason Hero shouldn't be allowed to compete.