Where you need even more privacy, don't use email. Even if you self-host with good OPSEC, use SimpleX instead.
Where it's mission critical, don't use the internet at all, use good OPSEC and communicate in person.
What’s wrong with an unsecured channel with strong cryptography, say GPG?
One thing to add ava, communicate in rooms without electronic devices 🥸
💯 That falls under "good OPSEC"
I realize how often people (myself included) choose convenience over privacy, and I hate that.
It depends on your threat model in each area of your life. Tradeoffs are a natural occurance. The most important thing is to do the work and know your threat model.