The thing I found funniest about Harry’s method of resurrection is that it wasn’t even specific to him. The way they brought back, say, Aunt May was stupid but at least they didn’t follow it with “also all these other dead characters were actors too”. The Mysterio explanation doesn’t just trivialize the characters brought back but it also makes Mysterio himself less of a character and more of a plot device.
The reasons behind bringing Harry back are equally laughable. It would have worked if it had happened at the end of the Clone Saga as planned because that was born out of a writer saying “I have an idea for this character”. No one in OMD had any idea what to do with Harry and I doubt he’d have come back if not for the EiC ordering it.