Yes, a member of the communist party cadre in certain historical times was separated from the workers they represented. They were full time revolutionaries, no longer part of the working class. This was one of the main issues (in my opinion) with the USSR.
In modern socialist revolutions, the representation must not be separated from the working class. Though, I am also more supportive of tendencies that uphold grassroots democratic behavior. See Rojava for more interesting ideas on that.
The system you are talking about sounds like a cross between a direct democracy and a post-scarcity communist society, if you've not read the works of Iain M Banks you should check them out, you are pretty much describing The Culture :).
Haven't read the others, but Red Mars is excellent, and better than Culture, in my opinion (though the latter varies in quality).
For another vision of a futuristic post-scarcity anarchist adhocracy, see James P. Hogan's Voyage from Yesteryear, which features less "magical" AI and is more of a reflection on cultural conditioning.
But how is that justification any different from the ones proponents of free-market capitalist use to explain why our system is different from what they propose?
There's a difference between debating the merits of communism and the tactics to get there.
I think communism is better for people than free markets because markets run on competition, which is in stark contrast to mutual aid, which is how communism works. There are of course many other factors that go into why I think communism is better than free markets, but there's many other reading resources on that. There are also market socialists who oppose capitalism, but support free markets.
Within the left, there are many different tendencies that people have developed to get to some sort of socialist economic structure. The main one we've experienced in the 20th century is Marxism-Leninism. This was developed by Lenin, and basically issues in socialism by the proletariat seizing control of the state and using it to suppress the bourgeoisie until the class no longer exists, at which point, the proletarian state withers away and tada! Communism.
There are also anarchist movements that involved destroying the state at the same time as seizing the means of production. See Revolutionary Catalonia or currently Rojava for interesting movements in these veins.
There is also democratic socialism, which basically involves communist parties getting elected into the government and issuing legislative changes that move toward socialism. This tendency is not revolutionary, but evolutionary. This is sort-of what has been going on in France and Greece. My opinions on this tendency aren't favorable, but to each their own.
In modern socialist revolutions, the representation must not be separated from the working class. Though, I am also more supportive of tendencies that uphold grassroots democratic behavior. See Rojava for more interesting ideas on that.