TNG is very, very good, but it wears its heart on its sleeve. Picard never struggles with existential moral ambiguity. Even when he (rarely) fails, he's always The Good Man.
The utopian slant is appealing and we can't help cheering for him, but DS9 revealed there was some sleight of hand behind the narrative.
Of the series since, I think only Battlestar Galactica approached similar complexity. Maybe Westworld, which got quite abstract and interesting towards the end.
The Expanse is more by the numbers. It's basically class war in space, with the military, the aristocracy, and the peasants slugging it out, while a dragon rolls in and threatens to eat everything. The writing is very challenge -> response -> partial solution over and over, and for me it just doesn't have the depth or the emotional reach. (Or the acting chops.)