The problem with "private caller" is that a number of important calls, particularly health related or silent numbers come up as "private", so I end up answering and get a few scams or "charities" as well.
If the technology is capable I would prefer it came up with something like "Hospital" or "A. Smith" without disclosing the number. Our clinic & hospital contact us by phone to confirm appointments, if you don't respond, the appointment is cancelled. We have arranged with our one friend overseas to send a text before he rings, that's the only time we answer "overseas" calls. As I get calls, I look them up and if it has a spam rating, then I list it in the phone's phonebook and assign it a different ring - not to be answered. We exceeded 100 (the limit of the memory) and have bought a handset with 500, hoping it won't ever be filled. It really is a burden to have a landline.