Emails, password manager, VPN, and now documents—absolutely not a wise thing to do. Never put all your eggs in one basket; your whole personal and even professional life shouldn't be entrusted to a single company.
But I refuse to use their Pass app, and I similarly will refuse to use this new docs app. I use Standard Notes for all my notes (funny enough they joined with Proton this year lol) and Bitwarden for passwords. And then I just let Apple sync all my contacts, and for calendar it's kind of required that I use the ios calendars for family member sharing reasons.
Use a custom domain with ProtonMail or any other provider.
Frequently download email, calendar, etc. from Proton, Google, etc.
There are a lot of good comments in this whole conversation about nice to have Proton improvements, but I suggest we not lose sight of the benefits of not having personal and company data in the hands of Microsoft, Google, Amazon, etc.
Companies and individuals who aren’t worried about the costs and risks of the lack of privacy should not use Proton.
If you want to be more cautious, sure. But the likelyhood that they're going to collapse so hard and quickly that you lose anything significant is pretty slim.