'To be fair, the actual root idea of communism (with a small "c") where everybody shares property, and wealth is distributed equally amongst everybody, is a valid utopian ideal.'
No it isn't. It's valid only for people that aren't human and believe in equality of income under all circumstances.
In the real world, you'd better believe that people need motivation to make an effort with something, particularly if that's a role that is needed by society and cannot be left to the chance that someone will spontaneously decide it's their calling.
I don't intend to work for a second longer than I have to, and once retired will do projects that interest me, help people, but don't contribute to the fabric of our capitalistic society in the same way my current role does. The only thing stopping me doing that right now is the fact that the outlook for my pension is currently dire, despite paying in a reasonable proportion of my salary (to be fair, I am trying to retire at 55. I haven't looked in depths at the numbers recently as I don't think I'll like the answer).