Oh it's not impossible to beat. The solution is not to be caught dead with your character selection chip on Luigi, Mario, Samus, DK, or Bowser on the blind.
Easy.
If you ban, the 'problem' would go away in a vicious short-sighted sense. Yes, an obstacle to winning, for those who are set on using these characters to which they have fixated before the fact despite playability issues, is gone if the ban is done. But some people want the competition. Some people can dislike, that if you do this and give these characters a green light on the field, a pass against Dedede, then these characters will be unnecessarily cluttering the metagame. They'll get in the way of everyone else training to defeat the otherwise simplified field. Why give viability if they're. . . not viable? Moreover, Dedede's life will be harder, and so Dedede representation will go down.
A player could even want the tactic to remain because he wants to be the guy that beats it. The Ness user who finds EIDI for Marth release infinites, if one of those could show up for Luigi, I'm there there would be much rejoicing (and **** stroking 9_9).
Most worrying, these people would get anxious that other bans would occur. Modulo WastingPenguins distinction (which I'm not sure I get), this opens a can of worms where any good tactic may be at risk. Why use a great exploit if I can get banhammered? It's not a pleasant feeling.
Not all people would be happier. At the very least, there's still I'm sure some number of D3 mains themselves who would feel very shortchanged if their avenue to instant win were taken from them. Why increase the number of matches they have to deal with? Their character has game against five characters. That's a fraction of the cast you can simplify your training time against, and so credit to these players for picking up a character that can thus fold time upon working their matchups for the other 30~ characters. These guys made a move that is working out for them, it's unjustified to say you wouldn't be making them upset.
. . . wow I'm actually convincing myself this position is problematic now. The D3 infinite really might be an exception. I can't find a bad thing that would happen to the metagame in any sense, from either the position of being an infinited character or not, and whether I want money or whether my ultimate goal is 'seeing what I can beat.' There's just the effect on D3 mains themselves. Banning strictly increases diversity while removing nothing but the ability of players to cash in on the lack of diversity, thanks to WastingPenguins' distinction. Is not our notion of the competitive field one that lets in all comers who can take a route to make the challenger lose? Diversity is inherently a good thing, we agree, since a diverse field is one more challenging to someone trying to get to the top. We just commonly evaluate it as less good than other factors, or judge that we are unable to be objective in most cases between it and another 'good'.
But the D3 infinite creates a stunted asymmetry in five matchups, such that (a) it doesn't prove anything to play out the match in anything past noob level, (b) the move can be enforced out of gameplay with surgical precision just such that these uses where it is indeed infinite are gone - which happens to be the same as the uses where it makes the game trivial, and (c) there would be no glory in 'beating' the technique as one of the exploited characters, by the very nature of the mechanic: since it is a grab, either something equally strange will be found that allows people to 'glide farther' before regrab, or people will just learn advanced methods of "Don't get grabbed." There is nothing else to beating it, it is a one-dimensional technique. (This point and the first point are what the D3 sentiment of banning the move is grounded in, I think).
Leaving it to people to take this technique as a challenge does only this thing: it makes people give up on using these characters, at least in this matchup. As two consequences of that, (i) the technique never in fact comes into play, because no one (who is smart) goes into the match to let people use it, and (ii) Players of these characters are discouraged from taking the character's game to a higher level, since there is such a devastating CP; and so the characters are effectively removed from the player's choices.
The game has five less characters. But there is something the community can do which will do just these things: Diversify the field, give D3's five interesting problems to think about, let D3's enjoy beating five more characters, and let the people who like these characters march boldly forward with their character meta again.
This sounds all upside to me. I think it objectively *is* all upside, and that's the important reason why I'm now questioning this:
Maybe it's a principled exception to the ban principle, as in, the rule for ban is incomplete.
D3 has 'fractured' the meta, and it satisfies conditions which, in my inspection, only make the game worse from every direction we respect.