Is it possible to make a game too hard?
Yes. Absolutely. It’s easy even. Just make a game where you need to do something that highly skilled people have trouble doing consistently multiple times in a row, like pressing a button on a 1 frame window, also releasing it on that frame, like 6 times, spread semi-randomly across a second. This is an extreme example, but it’s not hard to imagine more concrete ones.
On a more practical level, games need scaffolding for players. They need a difficulty curve for practical reasons. You can’t start someone off on the hardest combo trial, you gotta have them build their way up.
This is part of why depth is nice, because in deep games, there are a lot of ways to succeed. This means that if you can’t beat a challenge straight up, you can try it from another angle. Maybe you’re winning neutral a lot, but your punishes are really weak, so you can step that up. Maybe you’re not using your healing items as efficiently as possible. Maybe you’re taking too much damage in your focus to output damage. Should try the route on top versus the bottom, could try pressing the buttons a different way. This allows people to succeed at small things, even if they can’t beat the overall challenge, they can still see that they’re making some kind of progress, and there’s significant variation between each time they attempt.
Even back in the combo trial example, because combo trials don’t really have any depth if you consider them by themselves. They’re a straight up, do this really hard and specific thing, or you fail. If you just hand someone the hardest trial, they’re going to have trouble with even the first cancel or loop. If you work your way up through the trials, then it builds your skill, allowing you to begin tackling the harder ones, or even do better at combo trials in other games.
Probably the real mistake isn’t making something too hard, it’s not placing anything easier around it.