It's not a matter of people thinking they know better, but a matter of people seeing which approach makes them more money. Internet advertising is based on a bidding system which is highly tracked.

Advertisers may be bidding too highly on "targeted" demographics, but that's outside the issues of organizations like New York Times. Its in NYT's best interest to get the highest bids possible.

They may have been monitoring the difference in ad prices between highly targeted and not, and decided the difference no longer worth it.