I do think that some of Marx' thoughts still have some value today. But we have to take into consideration the historical situation when they rote their works. In the middle of the 19th century, it was pretty clear that a small group of people which you can call the bourgeoisie "bought" the laws. Women had no voting rights, there were slaves in the US and in Russia, in Prussia the weight of the vote depended on how much taxes you paid.
Things have changed a lot, and nowadays you can't just buy power as easily as then, even if you're wealthy. However, there's a tipping point where the amount of fortune can be used politically. And after the January supreme court decision, it will be a lot easier in the US to behave like Don Corleone ("Give it to a Jew congressman.")

The problem with all the socialist experiments so far (or those who called themselves socialist) is that none of them respected freedom of speech or political opposition. And this includes Lenin and Trotsky.

It would have been interesting where Allende's experiment had lead to, if he hadn't made some foolish choices and if Pinochet and his allies hadn't destroyed every bit of freedom and social justice.