Karl Marx praised capitalism as an upgrade from feudalism, and for it's effect on the advancement of technology. It's obvious that capitalism was a step up from feudalism, but that's not the point.

The point is that capitalism eventually evolves to a stage where it is worse for civilization as a whole, than it is beneficial, and we are at that stage now(have been for a long time). We are depleting all of the Earth's resources at a very unsustainable rate, and wealth inequality is back to the point where it was with feudalism, if not worse.

You brought up a good point that no one is asking for a return to past systems. We are looking to evolve to a system that will sustain us as a species, long term. Some people can't understand that Capitalism won't work forever, and it will eventually destroy us. We have had smart people telling us this for hundreds of years now, too.