I would rate it as "almost communist" if we are going by a Marxist view because it still has a state. The state that exists appears to have two functions:

• To provide centralized infrastructure and services like schooling.

• To provide a military for defense against (primarily) external forces.

In a sense, the society if Star Trek has the federation being analogous to a bloc of socialist countries that still has to deal with a bloc of non-socialist countries that are sometimes aggressive. Star Trek itself has usually focused on telling stories about present humanity through a lens that operates on an interstellar scale. Aliens as standins for other cultures. An advanced egalitarian federation society that critiques current issues. The aggressive neighbors in star trek sometimes fulfill the sane roles.

So you could say that the federation is just part of a much wider society of sapient creatures across the galaxy, some of which are even capitalist, so society-wide communism is certainly not achieved. But rather than export revolution as socialists, the federation is highly passive in its approach to spreading its political program. In addition, leaders in the federation do not use the terminology of socialists nor do they seem very familiar with revolutionary thought. They seem to have adopted idealistic attitudes in their post-scarcity society, seemingly one where the economy is not thought of as an important or complex system needing critique.

Though again Star Trek is mostly a universe meant for telling stories about humanity as it is now. A proper commie would be explaining the problems of capitalism via the show.