The big thing that separates utopian from scientific socialism for me is that the utopian tries to abolish contradiction as an idea while scientific socialism analyses and resolves specific contradictions but understands that they're inherent to any kind of relationship. Marxists chase the least-wrong solution through experimentally attacking existing dialectics rather than trying to create the perfect one out of simple agreement.
The big thing that separates utopian from scientific socialism for me is that the utopian tries to abolish contradiction as an idea while scientific socialism analyses and resolves specific contradictions but understands that they're inherent to any kind of relationship. Marxists chase the least-wrong solution through experimentally attacking existing dialectics rather than trying to create the perfect one out of simple agreement.