I think I beat all of the non optional content in Celeste in non-assisit mode, but a lot of the difficult optional content becomes much more tolerable with assist mode. Even just setting it to 90% speed is amazing. My reflexes aren't great, and more importantly I don't have as much time as I used to. I don't want to spend hours trying to beat an optional challenge. They're still challenging at 90% speed in assist mode, but they don't take me hours to do.
Dungeon of the Endless you should try Easy mode because it's actually the normal mode lol. The easy mode is called Too Easy. Those are the only two difficulties (apart from a different world gen setting thingy).
I think people get too caught up on what difficulty you should play. If you get frustrated, turn the difficulty down. Then, if you get bored, turn it back up.
A game that gets a huge thumbs down from me is Resident Evil Village. I died a lot early on because I didn't understand the game and hadn't played a console fps in forever (and there was a graphical glitch making everything grayscale). The game asked me if I wanted to go to easy mode. I finally did. Once I got the hang of it I was ready to increase it back. NOPE! You can only go down to easy mode and then never change it ever. The reason this pisses me off is because are we so concerned with bragging about accomplishments in single player games that we remove useful features? Why? Who cares! I get the same anger towards and rogue like game that doesn't have a save and quit feature because they're worried about people save scumming. Oh boo hoo, maybe someone save scummed to beat the games, who cares? Sometimes shit comes up and I need to stop playing. I'd rather not have to throw away a whole run than worry about people saying they beat the game but save scummed their way to it.