Star Trek economy is all well and good and I think it is the eventual outcome, but in a specific time and place, with specific people and their baggage, the immediate best way forward may be something other than what I would prefer.
Didn't Marx say politics went through stages? Feudalism to capitalism to socialism or something? He might have had a really valid point on this. We can't jump from primitive barter economies to interstellar travel.
Besides, even though I like certain ideologies, I can't help but see the practical on the ground results of faulty, corruptible humans trying to implement them and it seldom turns out for the good from what I've observed. I have to imagine we will get there over time, perhaps with non human AI at the helm.