I agree OP.
I have seen most of the Overwatch merchandise put out so far, and have played the game a decent amount, and everytime, i always come back to the fact that they put out all these amazing CGI shorts that are Disney quality with all these super inventive and unique characters full of charm and witt and a decent set up backstory, only to plop them down into a multiplayer arena to endlessly shoot at each other and rack up meaningless numbers, with the only lore in small doses outside of the game.
This game would have SLAYED even more so with a single player campaign atleast...i know people in Japan have been asking for an actual movie made out of Overwatch since the first cinematic trailer came out, they keep looking at it like Big hero Six meets Boku No Hero Academia.
Blizzard has the resources to make a fully featured game, they aren't some studio that's begging for cash either.
Its the same problem i have with games like Destiny and Titanfall, although i atleast understand Titanfall devs didn't have much money at the time.