Whatever movesets they were given for MSH would have been considered iconic, whether good design choices or not, only because of the characters themselves and them releasing so many games so fast in succession, that they couldn't change them up drastically. Iconic does not necessarily mean the best choices for the characters now, especially with so many characters being designed from scratch when much better tech is available and designers are much more creative.
Cap and Spidey were designed to kinda be like the Ryu and Ken in MSH. They each have a projectile, a hurricane kick-like move and an uppercut as their core moves. Their movesets were safe and pretty cookie-cutter for the time. Their movests are still being defined by one game/design team's decisions from a 20+ year-old game. I think it's fair to consider them OK for the time, but not now. Cap is not too bad, but Spider-Man could be so much more interesting if they rebooted him. Does anyone really care if Spider-Man keeps his Spider-sting? I loved MSH, and I wouldn't miss it. Maximum Spider was always pretty boring for a super move too. I don't think the designers necessarily game them the perfect core moves/style on the first try, so there's no need to keep clinging to them.