Because Metaknight's presence obviously overshadows those characters. Why play Peach when Metaknight ***** her? Why play Marth and Game and Watch when they have bad match ups against Metaknight? Why play King Dedede when again, it's a particularly hard match up for him? I understand his logic perfectly.
Because Peach is fun for some people. Because some people are good with Peach.
Because Marth is fun for some people. Because some people are good with Marth.
Because Game and Watch is fun for some people. Because some people are good with Game and Watch.
Because King Dedede is fun for some people. Because some people are good with King Dedede.
In your perfect on paper world, everyone would choose Meta Knight because he's the overall best option. And this would be true of all fighters; everyone would choose Fox because he's the overall best option in Melee, everyone would choose Sagat because he's the overall best option in SFIV, etc.
Here's the thing: people don't do that.
For a lot of good reasons, not everyone uses the character that gives them the best advantage. And this is why fighting games have more than one character, and there are able to be healthy competitive fighting game communities.
Some people like playing different people, or are just good with people. Some people suck with Meta Knight, even though he's the best option. Some people just don't have fun with Meta Knight, so they don't want to play him on a competitive level. There are quite a bit of reasons for not choosing the best option in the game.
Or maybe they think they're actually viable characters, or they think their match-up vs. MK is winnable, or better than what most people think. Match-ups are subjective anyway. There's no way to objectively say, "Wario vs. Diddy is 55:45," because of differing opinions. At any rate, 6:4 match-ups are certainly winnable. They're winnable in every other instance, except, of course, when talking of the MK ban.
Why would you main a character with a bad match-up against Snake by that logic, as you're going to be encountering a lot of him in tournaments too? Oh wait, people don't think of that. Because he has a bad match-up, and on paper you can counterpick him, even though you'll never win against a competent Snake if you just counterpick D3 unless you've invested a lot of time in D3 to the point where he's almost your main if he isn't already.
Yeah, Luigi gets ***** by MK, but he gets ***** by a lot of top tier who's presence would only grow in the instance of a ban. Yeah, Jigglypuff loses to MK (and not even by that much), but she gets ***** bya lot of top tier who's presence would only grow in the instance of a ban. Yeah, Olimar loses soundly to MK. But he also loses more soundly to Peach, who's presence would only grow in the instance of a ban.
So I don't understand his logic.
So are you denying the fact that low tiers generally have a disadvantage in other fighting games, or are you denying the fact that there are other fighting games with a top character with at worst even match-ups with healthy competitive scenes?
Don't be silly.
The community was maybe 1/5 the size it is now and even back then it only took them about 10 months to find a way to knock Shiek down a peg. It's been a year and two months since Metaknight overtook Snake in rankings and nothing big has been discovered that has made Metaknight less effective that's still around. As I said earlier, Snake's grab release into utilt/ftilt was worked around as was Bowser's grab release "chain grab" as was Yoshi's grab release to fair spike at 40% as was Shiek's tilt lock as was the Ice Climbers' ice block lock as was Falco's lazer lock... and so on and so forth.
Diddy Kong.
To eliminate as much of these theorycraft numbers as possible, I'm going to say this.
Diddy Kong has known techs not often used at the top of his metagame. Single banana locking will propel him quite a bit, as will incorporating more instant throws, as will working out the kinks of mid-range pressure and zoning game (which is what made many of his match-ups easier, such as Marth which is widely accepted to be even now instead of one of his worst match-ups).
There is known room for him to improve in his match-up against MK. What known room does MK have to grow?