That's because it (no rules changes negatively affecting GM) became the race to mediocrity rather than superiority. But that's the nature of the beast - if you can't elevate one, you have to bring the others down. It could be argued that in the earliest days of PS that both Mopar and Ford - prior to weight breaks - were far ahead of the GMs and was why the rules changes went into effect "to create parity" before that was a catch phrase. But those were cars built with factory blocks and heads, and as the rules package relaxed restrictions on those requirements it helped GM become competitive. Today everything is aftermarket and most of the NA development over the past few decades has been on the GM-based platform, so everyone just rents one of those and throws it in a Camaro. The Brandon Millers, Alan Prusienskys, and Joe Wilczeks of the world have an uphill battle (Larry Morgan too, when he had the Ford) - yet I applaud their persistence while getting little or no factory support.