The later seasons let go of some of the Burnham stuff and let characters like Adira have their own plots. I believe Paul and Hugh also had a few arcs though I never got into them myself.
I just didn’t like early Burnham as a character. I didn’t like most of Sisko either. That doesn’t make a show bad, necessarily, but I felt like Discovery didn’t offer a whole lot of B plot/secondary characters to compensate. Without secondary perspectives to offset Sisko’s heavy moral/philosophical arc, I probably would’ve hated DS9 as well.
In the later seasons, Burnham became more nuanced by having Book as a sidekick, as well as fleshing out the crew a lot more. They were no longer hurdles in the way of Burnhams’s self redemption arc/current goal in life.
TNG also had their terrible episodes, but there were just a lot more of them. Season 1 of TNG got 26/22/26/26/26/26/26 episodes versus Discovery’s 15/14/13/13/10. There was also no single overarching plot, so Picard could play a flute and live the life of an alien for a whole episode without derailing any story plans. The “monster of the week” approach also helped inspire some real good moral and philosophical debate that would otherwise never would’ve been written into a single story, but also some of the most cringeworthy TV I’ve seen.
Somewhere in the middle of DS9 and Voyager, Star Trek started aiming towards broader plot lines. At first they were multiple seasons long (though some of them had to be smuggled past Berman), but with Enterprise they became per-season. This makes it very difficult to compare old and new Trek, or even early and late seasons of the same show, because the dynamic changed.