I've been using a custom domain (with G-Suite, or whatever they call it this week) for over 15 years and I couldn't be happier. If I ever want to move I can take all my accounts/emails/etc with me, I don't need to update any contacts with my new email. It's probably the best decision high-school-me made (buying a domain for my email).

One thing: Don't get cute. I considered buying "stran.ge" so I could have "josh@stran.ge" but thankfully sanity prevailed and I avoided years of saying "No not 'strange.com', 'stran.ge'". Make it easy to say over the phone to an underpaid call center employee.