The reason there were so many PrCs was because PrCs fill books you can sell to players. Later on, a single PrC could fill six pages or more, even though it had only 5 levels and was really boring.
Oh, I know why they did it. But I would rather have class books resembling t the 2e Complete Handbook and Green Ronin Master Class book (i.e, focused on examining a single class including an examination of different sources based on various cultural archetypes, literature, and TV/Film., showing how they can be built with existing tools (4e builds and UA class variants) and providing prepackaged examples, and various ways they can be worked into the game along with providing appropriate support material.
As a DM, I find this much more useful in designing campaigns.
I refuse to tolerate 1 build or 2 heritage feats for a class in one book and then another few in another book (I am looking at the 2e sorcerer).
Even the 4e Power Books were disappointing (albeit much less so than their 3e coutnerparts). Wow, 4 builds for the 4e Shaman in two books? Give me a book like Green Ronin's Shaman's Handbook. A 4e book covering all the versions of the rogue from the two Martial Powers books would have been awesome. Instead, 4e takes 3 books to cover the cunning rogue, the thug rogue, the acrobatic rogue and the sneaky rogue.
The 3e and 4e class supplement book models with PrC, Paragon Paths, and Epic Destinies to pad out books and parcelling class specific things among several books is not a model that I willing to support any longer. It is also why, regardless of how good a core system we get, I will be waiting a year to see how they handle class and race supplements before jumping in.