I like that DSC initially had a main character who wasn't Captain, and that Burnham and Saru were mostly-friendly rivals/competitors. I also prefer that they were senior officers rather than lower-deckers.
During the first season you had them under a Captain who was one extreme, like Lorca. Then in the second season, they were under Pike, who was the exact opposite. So we got to see how Burnham and Saru dealt with both types of Captains.
Then in the third season, Saru was Captain. He made some choices I really didn't agree with (i.e. making Tilly the First Officer). And in the fourth season we had Burnham as Captain, and we got see her apply what she learned in previous seasons and what it was like to be on the opposite side of power-dynamic.
Finally, in the fifth season, Burnham is a more experienced Captain, and she gets to give Rayner a second chance, just like she was given a second chance, and Saru was able to advance in a field that suited him better. He makes for a better Ambassador than Captain, IMO.
So, Discovery's top two characters progressed in a way that befit them and in a way that Lower Decks wouldn't have allowed. Mariner and Boimler essentially end their series, kind-of/sort-of, the way Burnham and Saru started theirs.
Glad I got that out while I still had time. Crammed day today. Happy Holidays!