Personally, I pretty much never answer calls from unknown numbers, unless I am specifically expecting a call (eg: from a service company coming to the house, or calling back about an inquiry I made).
It's really rare I even get a call from someone in my contact list - even for something "urgent" most people just send a text ("call me - urgent!" is serious). Anything for work is scheduled, and even then it's been years since it was anything but zoom/teams/etc.
Part of this I think is a shift in the way people operate with technology: texting is faster and better than voicemail. Slack, zoom, etc dominate workplaces. Part is it's been ruined by spam.
I don't know if society as a whole is there yet, but I think it's basically rude to expect you can just interrupt someone at any point and demand their direct attention to have a synchronous voice conversation with you. Had the PSTN not existed and you were to try to launch "Telephone" as an app today, it would almost certainly fail. "You get a unique 10 digit number and if anyone types it in, it makes your device ring loudly, 24/7, no matter what else you're doing, and you're instantly placed in a two-way audio call with them!"