What happened was Mao died in 1976 and Deng took power. The following relaxation and stabilization of China, and its ensuing economic growth, is something the USA had no ability to stop.
That is what you don't understand. You think seem that if Nixon hadn't established a relationship with China, China's population would have just stayed face-down in the dirt forever, doing nothing, getting murdered in appalling numbers, etc. We had no power to stop Mao from dying or prevent Deng from steering China away from endless chaos and into making steel, textiles, and other low-end commodities that they began exporting in the late 70s and 80s. They weren't stealing US IP en masse until the 1990s after they bribed Clinton. Without Nixon, all that would have happened is China's rise would have strengthened the Soviet economy, as it would have been Moscow alone, not Moscow and Washington, influencing Beijing.
China would have risen as a player wholly hostile to America. It's something we couldn't have afforded against the backdrop of the Cold War.