A prefigurative politics is essential. In parliamentary proceedings you always get less than you aim for; even in a revolutionary uprising there are counter-revolutionary forces pushing back against you.

You can't just say "relax, man, the contradictions will resolve themselves". You actually have to go out and agitate for them! It is not utopian to say that on the line from (x1, y1) to (x2, y2), there is going to be at least one point where the slope is (y2-y1 / x2-x1). What is utopian is thinking that we can engage with the world within the "acceptable" window (range of slope) of what currently exists, and expect to get somewhere new with it. The human brain has limitations to what it can imagine, that are tied to what the individual's full range of experience is! The wider and more groundbreaking the range of experience, the more we'll be able to imagine.

Actually run lots of different tests to see how things work. *Expand your empirical basis as well as your theoretical basis. There you go, some real "scientific socialism".