BRILLIANT
Well... it has advantages, for sure. Also drawbacks. A custom domain, that ties together all your separate email addresses.
There are let's say 16 addresses on mysuperbestnumberonemail dot com. One used at a bank, one on a shopping site, 4 on a social media site, and one each at some utilities. Those are the ONLY uses of that domain for email in the whole world.
Where if it's a domain millions of others use, then addresses are harder to pinpoint down to one person.
That might matter to someone. Or it might not. Depends on what you care about. Just something to be aware of. A custom domain is a huge fingerprinting signal.