When telling a war story, this isn't unusual.
Even though DS9 remains my favorite Trek, it did indeed suffer from "small universe syndrome" near the end of its run. Sisko becomes a literal god. Rom is Grand Negus. Martok is Chancelor of the Klingon Empire. Odo saves his people, etc. Not to mention things like Weyoun being cloned many times to excuse him popping up over and over again. But even so, it generally did better than Discovery has to date - perhaps because it was the most truly "ensemble" of all of the Treks, and it had the largest set of recurring guest characters in the franchise.
Enterprise's attempt to do "epic" didn't work as well, but at least the story was somewhat plausibly constrained by having the NX-01 isolated in a different region of space from the Federation - along with the ship not engaging much in heavy combat directly.
While I think Discovery to date has done serialization better than Enterprise did in Season 3, I think ENT season 3 still felt broader and more expansive than what DIS is trying to do.