The author has completely missed the MAIN reason the campaign was good in 2009 and isn’t, now.
In 2009 the mindset was still that you needed a good single player game to get sales of a game. By 2015 call of duty had it figured out that they could almost completely ignore shoestringing a half asked campaign together and still get massive sales because their players were buying it for the multi-player, and all the money to be made by their fan boys buying it was in the multi-player.