Get an email address that you own, on a domain you control. Switch to a provider that takes your money for whom you are the customer - not the product.
I did this with Fastmail and Iki.fi, a Finnish non-profit[1], who have been selling people "permanent" email addresses since 1995.
But I still use my old gmail for one thing: Point of contact for the my domain registrar. Do you have any suggestions for how I can solve this?
With it, I have email from multiple domains doing what I want. I also have a <username>@fastmail.fm which has only been provided to one person: my domain registrar.
If you pay someone to handle your email this is a good approach, IMO.