WarCraft 1 being the setting is not the problem. It could have been a great natural place to start, but in the end everything still depends on having writing and casting for individual characters to draw an audience in. The character writing was just bad. The casting (on the human side) was also not good.
Also, everyone should pause for a moment to reflect on the fact that one of the biggest benefits to starting at WarCraft 1 is that you’ve got an unconventional ending (the humans lose) that sets up a strong need for a sequel. That doesn’t mean the good guys can’t have their own climactic victories, but it can happen in the context of an overall loss of the war. (Imagine a WarCraft 1 movie where the climax is the fall of Stormwind, and Lothar is racing to save the young prince Varian during the fall).
The fall of Stormwind adds fantastic dramatic tension for the creation of the Alliance and the looming threat of the Horde over the rest of the world. Just watch this old, old cinematic to the second RTS (mid-1990’s vintage). As cheesy as the old computer music is, and as bad as the graphics are, it still manages to give a sense of how Stormwind being destroyed pumps you up for this new “Alliance” that’s supposed to turn the tide.
With the movie we got, you don’t have the opportunity for this kind of sequel set-up. In the movie, the first war ended with a parade for the victorious humans.
They didn’t go through the loss of Stormwind, fleeing across the ocean, almost having Lordaeron’s capital taken, turning things around, returning across the ocean to Stormwind and fighting to the portal.
By having Llane succeed in destroying the portal in the first war, you also lose the cathartic-climax of the humans finally getting to destroy the dark portal as a triumphant army at the end of the second entry.
Yes, these are very cheesy cinematics when compared to the massive jump in quality of WC3, but it gives you a sense of the cinematic foundation of “Horde vs. Alliance” that the franchise was built on. WC 3 goes in a direction of, “Actually, Horde vs. Alliance is a distraction from the REAL threat.” That’s great for a third act in a franchise built off of rivalry, but arguably WC 1 really is the naturally best place to start.
But obviously not with the writing team this movie had. If they had been handed WC 3 as the time setting, I guarantee they’d have butchered it just as badly.