It also would likely be unplayable on most keyboards, as most (typewriter-style, not musical) keyboards can't handle large numbers of keys pressed at once.

I think subverting such game design paradigms can work rather well. I could mention Syobon Action again; while the game does have issues with slippery controls, the game's way of trolling the player makes it, in a way, a work of art. (Yes, the game will kill you for reasonable actions, but will do so in funny ways, and running out of lives doesn't yield a game over, so you can continue into the negatives.)

(Syobon Action does feel like a parody of the original Super Mario Bros..)

I've seen games, mostly WRPGs, that add gameplay mechanics that hurt quality of life without serving a useful gameplay function just for the sake of "realism". The Ultima series is a prime example of this (feeding in Ultima 7 being a particular egregious example), though it can also be seen in the Elder Scrolls series (weapon/armor durability when it's too easy to repair them, can't do things like mix potions (IIRC) or rest while in the air).

git gud

There is absolutely value in having one difficulty level. People can say they won the game and have it mean something. I ran a marathon, I got out of the electric chair, I rode the minecart to the lowest level of the sandstone caverns, I solved Gutei's riddle, I went North. This promises new players a sense of accomplishment which just might be the reason they buy the game. An entire new genre has sprung up over the decade to compete for the wallets of these "niche" players you call nonexistent.

Furthermore, communities form around "difficult" games, people help newbies, write and film tutorials, theorycraft builds, trade exploits, map out levels, plan smooth progressions. None of that would exist if the answer to "man this game is hard" is "there's a difficulty slider, you know".

Hard games? Difficult games? Are you sure you're replying to the same person? I made no mention of games that were too difficult, I was talking about games having a specific difficulty that is either too hard or too easy for the vast majority of players (note the difference, it is an important distinction, because even with these so-called 'difficult games', there will still always be people complaining that they're too easy). If simply being too difficult gave a game merit, then games would outdo each other in being difficult, until there was only 1 most difficult game with only 1 ever winner. Even the developers themselves know this is foolish.

A sense of accomplishment doesn't have to come to the detriment of someone else's enjoyment (unless one is a sadist, I suppose), and communities can form around many different things, not sure what that has to do with anything.

Yes.

> I made no mention of games that were too difficult, I was talking about games having a specific difficulty that is either too hard or too easy

Uh, what's the difference again?

Some games have a set difficulty, no levels or sliders.

Some of those are "too hard" for the vast majority of players - these are the ones that attract most of the complaints. There's value in these "too hard" niche games, people want to play them, people want to watch others winning or failing at them.

Others are "too easy" for the vast majority of players (typically children's adventure games). Hardly anyone complains about those (when people talk about dumbing down, they complain about broadening the appeal).

Yes, Dark Souls veterans complained Sekiro was too easy (they expected to have to git even gudder), they could predict all the fun in advance, and couldn't grief or be griefed and thus had no real reason to be afraid. It's still a "hard" game (and sadly too hard for me, cos 3d).