In American politics at least, there is a phenomenon of political issues that happen to have high popular support but also high political opposition. I call these "antipartisan" issues; and one interesting feature of these antipartisan issues is that they tend to get politically disengaged people to actually show up and lobby their representatives like nothing else.

Think things like right-to-repair, or data centers. A lot of people want right-to-repair, but a lot of politicians think IP law is untouchable and don't want to burn political capital on a battle they know they will lose when they can just sop up donor money to strike down or water down R2R bills. Same with data centers: they're unpopular with the electorate but politicians will do the scummiest tricks in the book to try and get a data center built. Eventually these kinds of issues do get some political wins, but they're swimming uphill both ways.

The problem isn't that democracy does not happen anymore, it's that our democratically elected representatives are unwilling to yield to democracy when the people wish to overrule them. The point of representative democracy is that the representative is supposed to do things in my best interest even if I don't particularly understand all the nuts and bolts. But a lot of representatives just think they got elected king and that my voice doesn't matter the moment I exit the polling place. This is, in effect, a deliberate attempt to disengage voters.

There's an old political cartoon from the post-Brexit era that goes something like, "These smug pilots have lost touch with regular passengers like us. Who thinks I should fly the plane"? The obvious joke being that no, randos are not qualified to fly the plane. But at the same time, the people who bought tickets are the ones who ultimately deciding where to fly. If the pilot said, "I know you bought a ticket for Miami, but I don't like Florida weather, so we're flying to Houston", you'd be right to be pissed off. The fact that you don't know how to fly the plane is not a moral vindication of the pilot's decision to override your travel decisions. Or, in this case, the fact that party leaders can out-organize their members does not mean they should overrule them.

As for the USSR, I had written a whole explainer on the French Revolution and how it neatly mirrored the Russian one before I realized it was distracting from my main point. It's easier to say "Russia is good at resisting change and coopting economic systems".

But if you want a stronger argument: The general pattern is that revolutions that intend to depose the ruling class of a country run the risk of turning on themselves. The infighting proceeds to burn through and kill all the true believers, leaving a hollow shell of people who played the power game well enough to survive. Thermidor[0] comes, and a coalition of surviving old guard and revolutionaries enjoy the spoils of a system whose dead wood just got killed off. And Russia did this twice: first, the Bolsheviks turned Communism into a dictatorship; second, the oligarchs turned "liberal" capitalism into an aristocracy. Inferring anything about the properties of the underlying economic system from how it was coopted by Russia is useless.

[0] The French Revolutionary Calendar month that covers late July through early August. Since nobody uses that calendar anymore, "Thermidor" generally means "the moment when the revolution is coopted".