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.)
It's kind of like Game of Thrones and 'The Red Wedding'. That episode is zomg, but if you watched it in isolation with no knowledge of the character arcs to date, it'd probably be interesting, but wouldn't have anywhere near the same sort of punch.
I find this amusing, because of what his best friend said about him wearing his heart on his sleeve :
Recently, and in no small part thanks to everything being available for streaming, I started with the DS9 pilot and made my way through all seven seasons. It took me several years of steady chipping away (spikes in watching on long flights, and weeks or months of no watching), but I thoroughly enjoyed it. There are multiple sharks jumped. Alien sharks jumped. The same hammy and even adolescent takes on relationships. But through it all shines the enduring, consistent introspective existentialism.
I think watching DS9 in this way provides a richer experience while TNG can mostly be enjoyed by dropping in here or there, and you eventually pick up on the long arcs of the Borg, Q, etc...