Should a level be solvable on the first attempt?

[AdrenalinDragon]

Sometimes levels are not designed to be done on the first try. The prime example being Lead Us Not into Temptation at a guess, because in my eyes it relies on the concept of trial and error. Hard levels which are theoretically possibly on a first try, like Avalanche are good but players are pressured by the time limit of 999 seconds, so it's tough to do first try without any guidance. It doesn't have to be a requirement to be a standout level though, just it might be considered easier when there's no guesswork to do.

I don't mind either way, as long as the level is fun and doesn't outstay its welcome for too long like Old Frog. That level is a bad one for that reason for me.