Before that USSR collapsed under Gorbachev. Why? They simply lost with their planned economy where nobody wants to take a risk. Because (1) it's not rewarding, (2) no individual has enough resources (3) to get thing moving they will have to convince a lot of bureaucrats who don't want to take a risk. They moved forward thanks to few exceptional people. But there wasn't as many willing to take a risk as in 'rotting' capitalism. Don't know why, but leaders didn't see Chinese way. Probably they were busy with internal rats fights and didn't see what's in it for them.
My idea is that there are two extremes. On left side people can be happy like yogs. But they don't produce anything or move forward. On the right side is pure capitalism. Which is inhuman. The optimum is somewhere in between. With good life quality and fast progress. What happens when resources are shared too much and life is good? You can see it in Germany today. 80% of Ukrainian refugees don't works and don't want to.