Seems they're more obsessed with mimicking Google, now focusing on to the "Office" suite of apps. Contacts really is a glaring omission.
Discussion
And the quantitative approach of using feedback to drive their roadmap has created 3 contact-related requests in their top row 7, all of which were created 3+ years ago. They offered Proton Contacts inside of Proton Mail and called it a day.
https://protonmail.uservoice.com/forums/284483-proton-mail-calendar/filters/top