I believe that the infinites should be banned because they make the characters unviable.
HOWEVER, this is not JUST because they have a 100:0 against others, since the EASE OF USE seperates his INFINITES from Fox's sucky match-ups.
I know it has been argued time and time again that ease of use makes no matter in the competitive scene. I disagree. Ease of use is a factor in EFFECIENCY in learning it. The more efficent it is, the more likely people are to learn something they would otherwise not. Here's an example of DDD's infinite vs Pika owning Fox.
You're maining some random character, and you want to learn how to win as MANY matches as possible in the LEAST amount of time. Now, 100:0 match-ups are a quick way to win more matches. So, you look into 2 possibilities: Pika for Fox and DDD for the 5.
Pika counters Fox because of his entire playstyle; you would need to learn how to CG, how to QAC, how to get in a kill move, how to gimp, and Pikachu's playstyle in general in order to obtain that 100:0 matchup. You would have to spend a few days at minumum to practice all of these to gain that 90:10 matchup. Its basically a few days to win all your matchups for one character. HOWEVER, if you had spent that time practicing with your main, you could have gotten good enough to win more matches in GENERAL! Learning to play Pika is simply a lose-lose.
DDD counters the 5 because of his CG; you just need to learn to spam waddles till they come close, then its just cstick grab, pummel, down throw, repeat. It'll take you a few hours, maybe a day if you're super slow. You end up spending only a FEW hours to counter ALL matches with FIVE characters. This is MUCH more matches won than if you had just kept practicing with your main; its in YOUR FAVOR to learn DDD.
Now, this is a generaliation; some people might have a natural affinity for Pika, some people might still get 3 stocked as DDD against Mario. There are also other cases of 90:10, but they too, often are not worth the time, even if they only take a few hours to learn; DDD countering FIVE characters is what really makes it effecient. However, for MOST people, the only choice that would HELP them is to learn DDD JUST enough to win every match against the five. Therefore, assuming most people are smart; NEARLY EVERYONE should know how to use DDD well enough to counter the five, while BARELY ANYONE would learn Pika SOLELY to counter Fox.
Therefore, DDD's infinite simply changes the metagame and makes characters unviable like no other technique does.