We can't be sure about alternate timelines, but it's a strong possibility that, had the USSR been left in peace, it would have achieved an even greater prosperity by now. The USSR was on a path to moderation: Khrushchev was not Stalin, and Gorbachev was quite moderate (to a fault, some would say, given the results of his tactical mistakes). They might have actually achieved something like communism by now. We'll never know; we didn't let them find out.
I do agree that Russian jingoism was a problem with the Union, especially for "buffer states" (e.g., Poland, Hungary) whose citizens were treated badly in the midcentury. This likely would have moderated over time under socialism. (Under capitalism, for countries still within Russia's reach, it has not.) In fact, even in the SSRs considered "lesser" than Russia, approval for the USSR and the desire to remain were well over 50% even up to the point of dissolution. The people wanted to fix the Soviet Union, not break it.
As for the prosperity in Eastern Europe, that tends to be the case in countries remain mostly socialist, like Czechia. It's true that they have mostly escaped the horrors of the post-Soviet 1990s and 2000s. What is less clear is how stable their well-being is. I hope this forecast is wrong, but I'm afraid that the EU is not that far behind the US on the path to corrosion, corruption, and ruin. What is happening in the US, I'm afraid, is coming for everyone. Where do the worst people in the world--figurative reptilians, literal pedophiles--meet up every winter? Not in the US, but in Davos, Switzerland. This is a global problem.
Are the people of the FSU better off now than they would have been, had the USSR persisted? It's impossible to know for sure, but I think a strong case can be made that it would have developed a limited market economy, one that avoids our issues of extreme inequality but provides the benefits market systems can (e.g., increased consumer choice). Of course, the USSR did have a lot of problems, especially toward its end, though a number of those problems were caused by external forces (capitalist aggression). On that, and on the notion that capitalism's victory might itself be evidence of our economic model's superiority... I have strong doubts. History tells us that geographic and technological forces have more to do with which side wins a war than having the better economic system, and in the case of the Cold War, this was a matchup between a sea empire (capitalism) and a land empire (the USSR). A land empire has to try to assimilate people, which is hard; a sea empire can dominate them from afar (cf. Latin America). The Soviet Union started from behind, both because it had to integrate some very poor geographic regions, and because it bore the brunt of the casualties in World War II. It was never going to catch up, not unless we let it (which we didn't).
Although we can't know for sure what a 2022 Soviet Union would have looked like--Russia itself would probably be far less belligerent--we do have more than 30 years of data on the trajectory of capitalism, once this threat to it was vanquished... and those data are ugly. For at least two decades and arguably three, the reigning economic system has produced nothing but a devolving culture, absurd political polarization, and a collapsing standard of living.