Of course, there are indexes and indexes. Any lazy simpleton can make an index of proper names. The only good index is topical, and for my index, I value mesquite as highly as Brushy Creek and spurs as much as Spur Ranch. Though Dobie acknowledged that an index has far from universal appeal to readers, like the legendary 19th Century Ranger Capt. A bad index is better than no index at all, which makes a non-fiction book virtually worthless to anyone who does not have time to read it from cover to cover.
Librarians rightly disdain index-less titles.
But, to reduce Dobie's remark to simile, an index of nothing but names is skim milk compared to cream. Jonathan Swift certainly did. In the middle are indexes done for the titles of regional publishers, which often depend on the expertise of the person doing the index, assuming the publisher is willing to foot the bill for providing one. Most of the time, these publishers leave the it to the author to hire someone to prepare an index or to do it themselves. The results are usually mediocre.