As usual, the Star Trek replicator "post-scarcity" world believers ignore how to get there the most quickly, which is the freedom to innovate with free market economics, aided by university research.
If capitalism dies, it will be because of its own success in a world of freedom and free people have moved on, and not because some power hungry snot in government decides for it on its own behalf.
Properly speaking, capitalism is a corollary of freedom, in the economic world.
I dont think anyone disagrees. Free-market capitalism is great. It is a bit like natural selection. You get very robust and successful specimens out of the process.
The problem is that just like natural selection, shit can get a bit out of control. The old animals don't simply move over and let the new animals in. The world has to burn a bit. You get malthusian collapses and periods of starvation. Everything eventually settles down and equilibrium is reached(after a few hundred generations), but it isn't a smooth transition.
Also, just like natural selection, stuff gets completely out of control if you pump unlimited resources into an environment. Imagine you had an aquarium, and you started pumping it full of fish food. The fish aren't simply going to eat until they are full and then allow the other animals to thrive. The larger fish will gourge themselves. Some of them will gourge themselves to death if you aren't careful. They will grow huge. They will still attack all of the smaller fish that they can now fit in their mouth. It won't be because of any need for food, rather it will be a basic predatory instinct. They will use their new size to dominate the fish tank. Even with the unlimited food supply, they will still be attacking all of the other organisms in the aquarium. They will pick the aquarium clean, until you have nothing in the tank but a few massive fish. The massive fish wont even be able to swim.
No one is saying that natural selection/free-market is bad. In fact, it is very good. Evolutionary algorithms are some of the best in the world to solve difficult computer problems. The issue is that they are messy. They are incredibly messy. They will require many generations of destruction to reach equilibrium. That is fine if we are talking about bits of data. It can be a bit more dubious if we are talking about human lives. They also frequently come up with solutions which are very counter-intuitive and downright cruel. Once again, not so bad in some realms. Awful when discussing human beings. The solution to the problem is to keep some hand on the system and make sure that the experiment of the free-market doesn't get too crazy. We don't want 5-year-olds working in mines or people being sold as slaves, both of which are free-market solutions.
You can debate how much 'regulation' you want on that experiment, but don't pretend for a second you want a completely unregulated free market. I can promise you that a world without regulation would be very messy and very ugly. After a few thousand years, it might settle down, but in the meantime many millions of people would suffer. So the real debate is only how tightly you want to rein in the experiment.
Now, as far as a post-scarcity world:
You want to get there more quickly? Why?
We have no idea how to handle that transition and the transition will be ugly as fuck. Lets be honest, we are pretty much already to a post-scarcity world.
Right now, the total energy cost to build a solar power plant is less than the output of the solar power plant. What does that mean?
Hypothetically I could build a 1 MW solar plant, and then exclusively energy from that solar plant over the next 30 years to build a 1.2 MW plant. That would include the mining, refining, fabrication, feeding the workers, harvesting their food, etc.
Unfortunately, the gains are pretty minimal and without an energy market it doesn't quite work out right now. However, we are on the precipice of a world where energy is basically just limited to how much time we want to spend building solar/wind generation facilities. For all practical purposes, that is a "post-scarcity" world for basic needs.
So, how are we going to handle that?
We going to start giving away electricity? We going to let electricity costs slowly crater? Are we going to have a race to the bottom to see who can build the cheapest solar plants without govt subsidy? Do we have any coherent plan?