Own your domain name, with that you can go anywhere.
Once you become a paying customer the options are so much better and more comprehensive. And owning your domain let’s you do far more flexible things. Rent a VPS, install ftpd. No longer live with San Francisco imposed choices.
And since Gmail's inception, I've been using a forwarded pop (edit: I meant imap) address from a custom domain. I've been accessing my forwarded mail through Gmail for 15-ish years now. I remember there's some fiddling in the settings and you have to make sure when you respond to an email that it responds with your custom address. But I've never had an issue all these years, and if Gmail were to drop tomorrow, I still have all my mail.