Iron Man sacrificing or losing companies and suits and technologies happens all the time. That's why it's not the same. It happens all the time. He's the world's finest engineer. He'll find something else or bring back what he lost. That's his regular. Peter had that one-shot fall into his lap, used it to be the best version of himself he could be, and then at the end that meant giving it all up. Because powa and wesponshibilidy and blah blah blah. Not turning in the diploma isn't comparable to sacrificing the giant company as a countermove to the global fascist invasion, and he's a better character for being able to make that mistake when it ties into his fundamental flaw and he couldn't see the harm. Most people wouldn't.