They're pretty clear about what is encrypted:
https://protonmail.com/support/knowledge-base/what-is-encrypted/
https://protonmail.com/blog/protoncalendar-security-model/
Just because someone disagrees with you, does not make them a shill. Personally I do not use ProtonMail (though I have tested it thoroughly). I have a number of mail accounts, mailbox.org, disroot.org, and one hosted at privacytools.io.
That is not to say I think ProtonMail is a bad product however and have recommended it on numerous occasions to people both IRL and through PrivacyTools.