I see what you're saying but more isn't always better - at least not for everyone.
Like too much makeup, too much pepper, or whatever - it can be a turn off (or make you sick

). But let's think about this . . .
I would not want to limit you but neither do I want to be forced into using material I don't want. Just like you could argue for "don't use what you don't want to - It's your game!" so could I argue "make up what you think is missing - It's your game!".
I've seen more than one GM back off from running a game because potential players were furious he/she didn't use the classes or additional rules from book X, Y, or Z. When the GM tired to explain those were optional, arguments arose that they were included in the rulebook and if the GM was using section A then why not the PrC in section B? That wasn't fair!
This really becomes a problem when all the newer content that you want to use includes all the optional rules from the other new books (like NPC or monster stats from those books that you don't have). Core rulebook owners or those that wish to keep it simple can feel left out of enjoying the new material. Maybe you don't own 2 out of the 5 books you need to understand all the feats/PrC used in the newly published book. When I want to use the new book but not the others I feel like - "What a mess!"
We all know the GM must set the tone for the game and be the final judge of what is allowed - but maybe the publishers could help by putting out books that were sensitive to both views?
For example: Some books could be dedicated to operating strictly with the CORE rule book and other publications that are devoted to optional content. -- Or maybe even better -- Maybe some sections can be labeled as such: CORE material / Optional rules material. They could even have different versions of characters using the different rules! Core book Conan with his stats and PrC Conan in a different section. Choose the one that best fits your game! Core book section or Core book plus section for selected material that needs it. It would not be a hard thing to do I think.
That way you limit no one and don't make the purists feel left out for not wanting to jump on the "more stuff" bandwagon. Sometimes those that like the rules as given want more ideas too - just not more rules.
Just to add-
Wouldn't it be nice to see countless choices available for specific players to use while running their games without forcing others to make the same choices by making "official" game content based on these dozens of optional rulebooks?
I think both views can be accommodated here with some help from the publishers.
One weakness here is that someone can argue that they want extra rules A, B, and C but not D and E. ---- Well, you can't please everyone --- But a Core rules / Optional rules approach just might be a great selling point that pleases both sides of this issue.
I know I'd be more open to picking up the new books if this were so. More great ideas for me to use without all the clutter.
Anyway - just a few thoughts.
EDIT: Sorry about that J-Star. I guess we did sort of pull this off course.