I’m going the nostalgia route and playing Bioshock
Sure. By far the biggest issue is once you do it you are locked into using default iOS/MacOS mail apps. I’ve yet to find an alternative email client that can distinguish between your default iCloud account and your custom address.
Receiving email isn’t the issue, it’s replying from your custom address. I suppose a client that can use email aliases would work, but honestly I stopped looking for one on iOS.
I get people wanting an alternative Chromium based browser. Vivaldi, IMO, is a much better than Brave, and doesn’t have all the annoying crypto weirdness.
I don’t use either, though, I use Firefox