Umm, Stamets has changed greatly. Tilly is growing leaps and bounds. Michael has learned a lot. Even Lorca appears to have changed by the mid-season finale where he's looking beyond the war. Saru has learned more about himself and leadership and his relationship with Michael.
And, you're wrong about modern TV. Effective serialized shows like GoT and The Expanse develop both the plot and the characters. Exactly what Discovery is doing.
No, Discovery is not perfect. But, it is very entertaining and it has been developing the characters.
I dunno. I feel like characterization is far and away one of the weakest elements of Discovery. In general, the characters only "develop" to the extent needed to further the plot along - nothing more or less. There is nothing to Lorca other than his shadiness and mystery, for example. And nothing to Tyler other than the conflict caused by the Voq persona and the "relationship" with Burnham. While in general I think the last three episodes have been the best run of the series to date, they have been weak from a character standpoint, in that the previous few glimpses of normal life - things like Stamets brushing his teeth with Culber, or Tilly talking about her desire for command with Burnham - have fallen to the wayside. Tyler has been the only one given a
consistent arc, in that the rest of the cast is just doing what the story of the week requires - which in some cases can undercut what happened just before. Freaking Stamets - who is my favorite character on the show, because he was given the space to be a three-dimensional human being - has been reduced into being a plot device.
Obviously the series is just getting started, so it's difficult to compare with established shows with multiple seasons. But it's pretty clear on a show like Game of Thrones some characters get massive development (Jamie, the Hound, even Sam) when they aren't really super critical for the plot as a whole. Hell, you can even use Trek examples. Look at what DS9 did with Nog from the first to seventh season and tell me there wasn't some amazing character development taking place.
imagine the uproar if after last week's exploits capt killy/cadet tilly hadn't shown up yesterday
She still could have been given the single scene in the outfit over the holocommunicator. The problem was every other scene she was in this episode. Honestly the actress's worst work on the show to date, although she was given some terrible dialogue.
Agony booths, assassination attempts, keeping slaves, executions by spacing and nuking a whole planet to kill a couple rebels not enough?
No. The agony booths were only shown in the previous episode, and everything else is pretty bog-standard evil empire stuff which was the norm through much of human history. Engaging in a military strike against combatants isn't even that unusual at all. If they wanted to get squicky, they'd have things like more gruesome torture scenes, consumption of other sentient races, rape, etc.