I kind of doubt that showing the entire game counts as "free advertising." If anything, it counts as a walk through of the entire game which is filled with spoilers. The point of an ad is to show just enough footage so that it will tease the consumers enough for them to be curious about the rest of the game, not to show the entire game. And I dont believe that, outside of multiplayer centric games and esports, that lets plays have ever helped a fully priced AAA game. Of course it helps indie games cause a) they are cheap to buy b) they dont have really any marketing budget but AAA games are expensive by comparison and already have a marketing budget.
So overall, I think its nonsense that people are whining about it but of course they will whine since its the only way they will make money