A tactically-retarded old man who almost cost the player any hope of obtaining the Pillar of Creation in Stormheim (seriously, if we didn't stumble ass-first into Odyn we wouldn't have had any idea what the hell to do and would have had no logistical support or backup whatsoever) because he figured a global crisis was a good opportunity to go settle his grudge with Sylvanas, pulling the exact same idiocy Garrosh did in the Twilight Highlands with as much to show for it (namely, his johnson in one hand and a giant military blunder in the other), is not the sort of person I want to hand control of the Alliance's militaries.
edit: Not to say I think Anduin is cut out for the job right now. He definitely needs to learn more before he should be handed the Alliance's armies out of nepotism due to whom his father was. In the interim, that should go to the dwarves (who have a pretty good track record of getting shit done) until such a time as Anduin is able to competently lead the Alliance's forces.