The extended disappearing block sequence in Heat Man's Stage is way out of line on difficulty without Item 2, and you may not have Item 2 upon reaching it, which is garbage. Borderline impossible to clear without a lot of trial and error, even if you're really good at platforming, just by the nature of how the blocks work.
The laser stuff in Quick Man's stage is way harder without the Flash Stopper, but again, you may not have that. This one may be even worse than Heat Man because the lasers just sorta come out instantly and explode you-- you at least have some time to digest the Heat Man stage.
The Wily boss that can only be killed with Crash Bombs which needs your entire meter and doesn't have any meter refills outside the room. So if you screw it up once you get game over, and you can actually have an impossible to beat boss even without making any mistakes if you don't go in with a full meter. Never mind that if you don't know what to do at first you may screw it up even if you enter the room with a full meter.
I don't feel MM3 really has anything like any of these. If it has annoying stuff that depends on having a certain Rush Jet or whatever p sure that's all in Wily's Castle where you'll have everything at least. I guess it's long but whatever. In a first playthrough type environment I'd call MM3 way less jerky than MM2.
the game requires experience and prior knowledge. Youre intended to play the levels until you understand them and can beat them. its an execution-based puzzle game you see. The disappearing blocks you play until you understand the pattern, the big dumb lasers are the same way. Item No. 2 and Time Stopper are creative circumventions of those puzzles, but theyre not the intended solutions.
Crash Bomb thing i totally get your complaints but like just play the level again once you know the secret and win i mean it was like 1980 something how many games do you even have