A great deal of TNG makes me cringe after season three. Riker is essentially dead as a character, Picard becomes increasingly self-righteous, both Crushers are intolerable, Troi has very little to do until season six, and Geordi never gets any real character development outside of failed romances and a dead parent. Worf is the only character to get true character growth that lasts, but most of that happens in DS9.
IMHO, season 5 starts the increasingly steep slope of suckage:
Riker often is a stick figure, with rare examples of "The Pegasus" showing more (and kudos for the story making his background fit in really well with what was shown in seven years!).
Picard definitely became increasingly pompous - he was
Flandersized except he's still, what's the phrase... "po-faced"... as opposed to being overtly and/or 4th-wall jokey, so it could be much worse.
Troi rarely had anything expansive until "Face of the Enemy", which feels like whiplash as to how quickly she compensates from six years of what amounts to "He's saying the obvious", though I will readily bring up Farpoint, Ensigns of Command, Picard season 3's stories, and others where she is given something genuinely useful and cool to say or do that only Troi could do - heck, without Troi, Q would have won the Farpoint test. It didn't help that Guinan was pretty much Troi's trope, but Guinan also had a more interesting origin - left untouched until GEN and PIC fumbled with it, IMHO. But uneven scripting over the years aside, Troi was a significant character - the series could have shown more of it and without repetitive dialogue as often as they had.
Dr Crusher was hard to write for - combining a sense of authority mixed with compassion. I recall she was good in "Symbiosis" (fair dialogue, terrific acting of it), but in other episodes the dialogue she got was dire. "I, Borg" and "Ethics" come to mind as far as showing a caricature, reminding me too quickly how much better Pulaski was (IMHO). However, Picard 3's stories utilizing Dr Crusher are as thoughtful and commendable in scripting and I'll justify the pew-pew weapons scene at the start of that season since Starfleet training includes knowing how to use 'em and she's done so in TBOBW and other stories too.
So having spoken of teh Flanders, it gets better: Wesley is the
anti-Flanders, for the most part. He stopped being a magic wand stick figure caricature as early as season 2, if not "Coming of Age" being the earliest example of him being an actual character. He left the show before it slalomed, but - despite season 5 making him a hero before making him an egoist - his season 7 entry is still pretty dire. If Wesley wasn't the ship saver all the time, his actions with the diamond slot formation to show how great he was would have been more interesting as then he'd not be being a showoff but trying to show he's just as good as the seasoned adults (which I think was the idea behind season 1, but was written as Wonderboy sans cape flowing.)
Geordi -- I easily appreciated his technical prowess but being unable to get hitched. It'd be very boring as well if the show just showed successful domestics. TNG's range of characters made it easier for most of the audience to get to relate to some personality tropes.
Worf - am happy that the best of it happened in DS9, the one show that could actually explore him and Klingon lore in far more engaging ways. "Sons of Mogh", quick ending aside, is something TNG could never have begun to do. True, Worf's transition into DS9 starts with a partial copy/paste of what transpired in season 4 with wanting to resign from Starfleet in "Redemption", but DS9 quickly and successfully made it more substantial and gave him a life of his own.