He's actually right about this.
Serialized shows need an overreaching hook if they want to be interesting.
nBSG had "will they survive", "who are the final five", and "what's going on with the 13th colony".
Lost had, what the hell is going on with the island.
STD doesn't have any of that, we know how the war will end, we know the spore drive will go nowhere, and those are the over reaching plot-lines they choose to go with for the series.
You have a point, Discovery doesn't have the same unknowables as BSG or Lost but I kinda look at as being akin to Titanic. Yes everyone knew the ship sank but it was the events going on board ship that drew everyone (except for me, I hated Titanic). People Liked the love story, Billy Zane's wig provided the mystery etc.. It was the journey of the characters that mattered. Sure we know the Klingon war will end either with a stalemate or federation victory, but we don't know what goes into that outcome, does someone make a great sacrifice, do we reach a common ground with the Klingons or do we beat them with force? Same with the spore drive, yes we know it will fail, but does it fail because using it could it rip apart the universe, Will stamets die because of it? There are a large number of unknowns within the known.