For me the key feature(s) I want that Proton doesn't have is the docs and spreadsheets. If you're already on Google Suites/apps it's hard to move over without those.
If you want secure email on Google you can always use GPG with IMAP or Mailvelope. Additionally, for Drive storage you can use rclone with a crypt overlay.
It's more I don't want to use Google than I want secure email or secure services.
It's a much better value than ProtonMail
Use something like Fastmail. Perfect middle ground.
Another vote for Fastmail.
This is actually the next step for ProtonDrive in the future.