Comment by palata

It took me 20 years with Gmail to realise that I had screwed up by not starting with a custom domain.

When I finally changed, it was a lot easier than I thought. I just gradually migrated my accounts everywhere. I still have my old Gmail address, but I almost don't use it anymore.

Also (but I didn't try), couldn't you setup your own domain with Gmail? So that you still have everything in Gmail while you migrate all your accounts... but honestly for me it was really fine to deal with two email addresses for a while.