You may have to temper your expectations. Free usually means "sells/uses your data to offset costs". If you're OK with that, there's no need to switch off of GMail. If you're not OK with that, you'll have to pay.

Also, hosting email under your own domain gives you the freedom to move from one email provider to another even if they do shut down.

I put my money where my mouth is. I wanted to degoogle and so pay $50/year for Fastmail. One feature I like is automatically snoozing certain emails. Most of my non-personal email is automatically snoozed until 6pm every day. This way I don't get multiple notifications throughout the day for emails that aren't time sensitive.