It's not an all or nothing situation, far from it.
Platforms like Twitch definitely help to hype new games and make good free advertising. Most companies should leverage this. For someone who works in the video game industry, I do see the value in that.
On the other hand, it can be harmful for certain types of games (linear/story driven, like pointed out).
Not only that, but I think the way the revenues from those streams are shared is very unfair.
Think about it; this market is growing and the pie is getting bigger. Yet, right now the money is split only between the platform service and the streamer, either by advertising or donations, but without anything to the IP owner.
Movie and music organisations like MPAA and RIAA have taken very agressive stance against digital copyright infringement since the millenium.
Video game industry has been more forgivable so far, but doesn't mean it won't take a stand eventually.