I don't think the problem is difficulty, if frustrating aspects of the game are reduced then people won't quit so fast. Especially because the first level has the hardest obstacle in the entire game (the pit), it can be a brutal place to learn stuff like "wrong dialogue choices make you re-do the stage" or that jumping off the edges of platforms is very unforgiving (you'll often fail to jump, slip and die)
For later traps though, some of them are very hard to predict because you don't have the time to sit and observe when they'll change directions or appear. For cannons and vases, the projectiles feel like they can last too long and can still be chasing you on the other side of the map (mostly just on the last level though), at the very least let kicking dissipate the projectiles since kicking doesn't seem to serve much useful purpose outside of the boss fight and the one single slime corridor before the boss fight.
(Edit: I just saw part of the video of the other guy playing it and they kick a lot. I don't get why you'd do that when none of the enemies you can kick pose a threat you can't just jump past. I actually like that you can play the game with nothing but the arrow keys and the jump button, spamming kick to kill slimes isn't as fun as timing jumps.)
As for the boss fight, the boss can chain together the vertical-scrolling-left-to-right attack over and over without giving you any time to attack which is frustrating even if you can avoid it perfectly. The dashing attack can come out of nowhere without warning, too, even though you have to get close to attack. There's a bug where perhaps I hit the boss as they started their vertical attack but a second attackable copy of them appeared briefly to attack during the vertical-scrolling-left-to-right attack. Didn't cause any serious issues, just odd. I'd be more fine with the vertical attack if the room was narrower so it didn't take so long to run back and forth and wait.
Best girl is either boss girl or cow-girl.