As a libertarian I have no problem with communism as Marx envisioned it: people spontaneously sharing because they feel like it.
That kind of communism is free.
The problem is when people use guns and governments to force others to “share” against their will. Marx believed that was a necessary step, that would produce the abundance that would allow people to relax and work spontaneously for the collective.
What Marx failed to understand is the most productive economic plan is letting people do what they want (free markets), and that what people want to do is trade.
Marx envisioned full public ownership and central planning, because markets had a natural tendency to centralize themselves. He was not about “sharing” but progressing beyond Capitalism. People want markets and trade now, like they wanted feudalism before the steam engine, but one day markets will subside in the same manner feudalism did.