Well, it's better than the the first season of TNG, so i enjoy it.
As for it being to dark: It shows us one of the darkest hours of the Federations existence: Their first war against the Klingons. Just like in DS9s war with the Founders we will see over the season if the Federation and Humanity will manage to not only survive but keeping their virtues intact.
Some speculate (black emblems, Designation Number 1031, ...) that it will show us the founding of Section 31. Chances are good.