My phone has been on DnD for over a year now. I have a (cheap) smart watch which vibrates on certain alerts like message, calendar, and phone and I can quickly glance and see that it’s something I don’t care about. I also ignore the calls from numbers not in my contacts if I notice them. In the time I’ve been doing this I don’t think a single person has left a message on my voicemail - validating my actions.