It's fair to say that, in terms of popular genres, the run and gun bullet hell style shooter often falls into the background. After all, the fact that these games generally have to exist on a 2d plane often means they can feel lacking in either graphics or gameplay, which can put many off.
Then, in stepped Cuphead in 2017, drastically changing modern perceptions about the limitations of this type of game. It was still as devilishly hard as the likes of Contra, sure, but it's delightful cartoon presentation meant that you could easily underestimate it at points.
Because the cutesy graphics don't change the fact that this game is hard. Better yet, it's hard in a type of way that a lot of gamers aren't acclimated to like an RPG or first-person shooter, and so it presents challenges that most simply aren't immediately prepared for.
If you finished all the bosses of the game first time then you're either a wizard, a cheater, or a being from the eight dimension, as it's simply one of those games you have to smash you face into until you learn where you're going wrong.