To dox someone with a phone book I need to know something about them. A phone number, a name, a place. At least one of those. Then I need to get a phone book for their area.
Or you simply call directory assistance and get the number from the operator. Seriously - it's hilariously easy to get help finding a number. I used to do it for university fundraising.
Doxxing on the Net is completely different. It's a person taking someone is is mostly anonymous and presenting that information to millions of people at once via a quick-n-ease form. Then those people can harass the victim in multiple ways, not just by mail and phone, but also on social media, find connections to their peers and harass them too, bother them by e-mail, swap them, etc.
Anyone who thinks looking someone up on a phone book is even remotely similar to doxxing obviously hasn't thought about how different the situation is, even for a second.
The difference is twofold today. One, it's easier to disseminate the info - once one person has done the legwork, it's just a post and everyone has it. Two, people can hide behind *their* anonymity to harass you from a distance, which makes them bolder (and lets more people do it, because they're too lazy to drive over and egg your house).
Doxxing is a problem; it's just not a *new* problem. Like patents, it's the same problem with "on the internet" attached to it.