There's a book that I read where Jerry Spiegel & Joel Shuster go on record on this topic. During the silent film era, there was an extremely famous celebrity who routinely walked around unnoticed with just a pair of glasses on just to have some normalcy & this inspired the glasses bit during the creative process of Superman.

The minute I read " update for a modern audience" I check out. There's no need to update something that's good. The reason Captain America worked in the MCU is that nothing changed from the source material. I'm ing on Gunn's Superman for no reason other than his claim that The Flash was the best. That kind of dishonesty is scary...