As much as I liked enterprise, it didn't resonate with the casual audience as much as the other Treks seemed to.
We hadn't had a "traditional" trek show set in the alpha quadrant since TNG ended in 1994. With DS9 being set on a space station, and more concerned with War, politics and religion than exploration and discovery, and Voyager being well... voyager.
What I think they should have done, is gone back to what worked best, have a ship of exploration, and it could have dealt with the aftermath of the dominion war, as well as using new technology that voyager had discovered.
you could have brought back classic trek villains like the tholians and the gorn, maybe pushed out into the beta quadrent.
As the only "improvements," in and of themselves, not likely
As demonstrated there, the downward slope of the dwindling ratings transcended each series individually. During those years, the whole TV part of the franchise was subject to the same overall trend, and it was down, down, down. Viewers were being shed all along in every series since TNG, at a steady, almost clock-like, rate.
I would have moved with the times too, cast an attractive younger actor as the captain, someone in the vein of a michael fassbender.
There were shows in that time period that did have much more stable ratings (just look at any of the successful long-running shows), so it's not completely out of the question that doing enough things differently in a prospective new series could have recaptured some or all of the audience shed since TNG. As to whether Fassbender alone could have stopped the bleeding, I sincerely doubt that. The changes required to stop the bleeding were likely numerous, and at an even more fundamental level than you're contemplating, I think.