Ron,
Good post, and something we need to think about.
I'd posit that rules creep hasn't been so much the issue as not reigning in development and loopholes. Going back to 2011, we've allowed Turbo valve springs, a larger jack pad, and that's about it, up until this year.
We even denied non-OEM headlight covers last year. We did allow a few more things this year, but still denied most, and have made an effort to carefully limit what we allowed (like the single option for the offset cam key).
As classes mature, people have more time time explore the limits of the rules, and develop the cars. This is where the "creep" comes in the that you have noticed, and I agree, it's an issue.
Ram air was legal from day one, but it wasn't exploited until a few years ago. In retrospect, I think we probably left this one pretty wide open. It's harder to fix later, but we are working on this on the other thread.
When headers were outlawed several years ago, it was assumed by most that the collector was part of that, but the rules left the collector an open loophole that was has only recently exploited. We made a conscious decision not to outlaw this, as the dyno cap was coming into place, and it was thought to be useful to allow the lower performing motors to come up to the dyno cap.
Of course the new tire(s) have affected this, as well. The area I have seen the most effort at the national level is chassis development. The bright spot is the fast guys in our class share what they learned - You see this more in our class than anywhere else. What other class has the guy who led much of the National Championship race using his data to coach his competitors?
So, moving forward, lets continue to help each other get faster, and we'll try an be vigilant about reigning things in. as they come up.