yeah you know in all honesty, the chased-by-unkillable-enemies schtick was the mechanic I liked the least - like - I was never very happy to see that show up in a level. I'm much more okay with levels where you have to juggle incapacitation e.g. the fish against progressing through other elements - mister candycane feels fine as an exceptional case, maybe he gets to stay unkillable, but reference something like the Angry Sun in SMB3 - use it sparingly, and once the player makes it through a sequence, give them a break for a bit, maybe don't just throw them right into another chased-by-unkillable-enemy thing.
I actually thought that was something that Celeste kind of messed up too - you'd just barely squeak through a real tough sequence of platforming maneuvers, only to be rewarded with another, probably even harder sequence - I just want a break to have fun platforming for a bit, man! 😅