Thinking about the long view, the number of ways Discovery has changed over the season as it has "retooled" is astounding. Let me list the ones I can think of off the top of my head:
- Any sense that Micheal Burnham being raised by Vulcans meant anything regarding her personality
- Any idea that Burnham had Klingon-related PTSD and/or might be a bit racist towards Klingons
- The tight narrative focus on Burnham. She used to be The Very Special Protagonist who solved everything and saved the day. Now she just leads the "A plot" each week, and is being led around by the nose by Georgiou and Lorca ATM
- Saru having any character traits whatsoever. He used to be a coward who was resentful towards Burnham, which was shitty characterization, but it was something. Now he's just a generic XO with no personality - only saved by Doug Jones's performance.
- Tilly changing from a very weird, possibly ASD character to just slightly adorkable
- The mysterious black badges and floating water seen in the third episode
- The idea that Discovery is a special science ship researching all kinds of black-ops tech, rather than just the spore-drive machine
- Stamets being a grumpy jerk
- Klingons speaking in their own language with subtitles
- The idea that the 24 houses of the Klingon Empire were going to actually mean something
- The "lower decks" concept. Originally Tilly was just in the show because she happened to be Burnham's roommate. Now she's doing officer-level work as a cadet just because she's a main cast member and must be doing something.
Some of this can be attributed in-universe to character growth, but IMHO that's headcannon, they were trying to tweak the show as each script was finished.
Regardless, a lot of this was a mess. It was abandoned mostly to put focus on the long-con of Gabriel Lorca and to a lesser extent Ash Tyler. Which is why the tiny, tiny bit of character work which had been done on Burnham, Saru, Stamets, and Tilly has fallen so far onto the back burner, at least IMHO.