I think the problem with modern Star Trek series is that they simply have terrible writing. DS9 produced some of the best TV ever with action/sci-fi blends, and it also did more dialogue driven scenarios phenomenally well. I think the thing that really drew people in to DS9/TNG is that the writers really seemed to understand people of all perspectives, and so were able to create highly compelling characters and stories.
For instance the various plot points in DS9 between Sisko and Eddington (like "For the Uniform") often have you starting to cheer for the 'bad guys', while really confusing the question of who the good guy and who the bad guy even is. DS9 even excels as 'humanizing' the Cardassians who are, on the surface at least, just an evil trope. And recent times in real life should emphasize, to the point of absurdity, that this is what people and situations are genuinely like.
But the modern Star Treks feel like they were written by people living in a bubble with minimal life experience. They rely on political tropes and diametrically opposed good/evil stuff that's utterly banal, and intellectually insulting. They actually do have some of the same writers as previous shows though, so I assume there must be production/directorial pressures that caused the shift in 'style.'
I always felt like the problem w/ DIS was that the story itself was just incredibly overdramatic. TNG has... I think really only one of these moments in Conspiracy where The Federation is taken over by alien parasites, and OK let's just blame the 80s for that. But, just Lorca's arc in DIS would be a series-long drama in the TNG years, but it's literally like 3 episodes. Tyler actually being Voq is _completely insane_, and is also like 4 episodes. Also Culber dies! But also comes back! Can you imagine Geordi killing Crusher (who is retrieved from idk, The Nexus after a few episodes a little shaken but also totally OK), Data being a secret Romulan who underwent bonkers like, bone shaving to look human (and is also completely "fixed" in a single episode) and Picard also having euthanized his entire former crew but generally being completely fine?
For a while I thought the acting was melodramatic, but I actually think it pairs really well with the truly crazymaking amount of wild shit that happens moment to moment in DIS. Burnham should be a PTSD shell, Tilly should've resigned her commission long ago, etc. etc.
Some TV shows are now being designed to be watched as background while the viewers are pecking away on their phones. Plots are simplified and repeated. Viewers are often shown and then told important points multiple times, just to make sure they don't miss them.
Discovery did this some of the time. There were episodes where they would show, then tell, then tell again all within a few minutes. Not every episode was done this way. I suspect they were experimenting and it did not go well. Anybody who was actually giving the show their full attention was bound to be irritated. Discovery was a low point in modern Trek for multiple reasons. They initially decided to forgo an ensemble cast and bet it all on a protagonist driven narrative. This severely limited the diversity of viewpoints in the first couple seasons. The writing was bad for entirely avoidable reasons. People who watch trek pay attention to the universe's rules. You can't beam through shields, you need to have a reason for why the away team can't be trivially beamed out of dangerous situations, etc.. The people writing Discovery did not bother to do this on a repeating and continual basis. Again, it was insulting to anyone who wasn't pecking away on their phone. I wouldn't say the writers for Discovery merely lacked life experience. They clearly hadn't bothered to watch previous Trek shows.
Strange New Worlds is better written, but a little too reliant on high concept for their most recent season. Every episode seems to have a gimmick. Still the cast is good and I look forward to them wrapping up Pike's story and, presumably, setting up a reboot of TOS.
Lower Decks is the best Trek show in recent memory. Thoroughly entertaining from start to finish. I can't recommend that one enough, just in case anyone skipped it because it was animated. Intelligent. Inventive. Hilarious. The people who made Lower Decks really put a lot of love into it.
Edit: I forgot to mention Picard, which is unforgivable. Some of the seasons were a little uneven, but some were fantastic and it was truly a treat to see Patrick Stewart as Picard one last time.