Every person who suffered through depression is gonna tell you that, to feel enticed to do something, there has to be some emotional reward connected to it

I was going to disagree on this, but I think it rather comes down to intrinsic vs extrinsic rewards. I ascribe my own depression largely to pursuing, sometimes unattainable, goals and wanting external reward or validation in return which I wasn’t getting. But that is based on an idea that attaining those rewards will bring happiness, which they often don’t. If happiness is always dependent on future reward you’ll never be happy in the present. Large part of overcoming depression, for me at least, is recognizing what you already have and finding contentment in that. Effort that’s not intrinsically rewarding isn’t worth doing, you just need to learn to enjoy the process and practices of self-care, learning and contributing to the well-being of the community. Does this sometimes involve hard labour? Of course, but when done in comradery I don’t think those things aren’t rewarding.

it’s a mathematical fact that not everyone who’d start scrubbing tubes on a starship could eventually get into high positions since there simply aren’t that many of those

And of course these positions aren’t attainable for all, but it doesn’t need to be a problem that they aren’t. This is only true in a system where we’re all competing for them, because those in ‘low’ positions struggle to attain fulfillment. Doesn’t need to be that way if we share the burdens of hard labour equally and ensure good standards of living for all. The total amount of actually productive labour needed is surprisingly low, so many people do work which doesn’t need doing and don’t contribute to relieving the burden on the working class