"What I don't get is how flying more often than 2-3 times per week to build time makes me a sellout"

It doesn't, where are you getting that idea?

"I understand instructing is a great way to build experience and I plan on doing that but don't you think that at some point past the 600TT mark a CFI's knowledge base is ready for more of a challenge... ready to move to the next level"

Yes. Everybody's "point" is different. I don't know where to draw the line but 250-400 hours isn't it before going to the right seat of a jet.

"What I don't understand is why using a school to further your knowledge is bad"

No idea what you mean by that.