This is my biggest gripe, consistently, with both Discovery and Picard.
The benefit of doing serialization IMHO is that you can do long-form plot and character arcs. Don't have the ideas to fill out an episode in season 5? Call back to a plot in Season 2, and develop it further! Think of the character growth someone like Nog showed across all of DS9.
But both Discovery and Picard basically press the reset button at the end of every season. Not only is there an artificial, self-contained crisis which is somehow 100% resolved in the finale, the hanging character threads aren't even expanded upon.
Witness the great disrespect they've given Raffi and Seven's relationship across Picard. They start holding hands at the end of Season 1, break up off camera between Seasons 1 and 2, slowly reconcile across season 2, and then break up off camera again between Seasons 2 and 3. The show should have used their relationship as a baseline element of the season, and worked it in, but instead it treated them like plot marionettes, hence it's irrelevant.
Picard's relationship with Laris is another example. Zaban dies off camera between Seasons 1 and 2 so they can have romantic tension (another case of the new showrunners having entirely new ideas). The whole of Season 2 was, if it was about anything, getting Picard to be open to a relationship with Laris, who is sidelined after a single scene in Episode 1! I can see how Picard's girlfriend would be hard to integrate into the season, and it's been like a week, but it would have been nice to have him at least send her a message or something? At least he hasn't been trying to get back with Beverly I suppose.