The problem is that TV and computers can be used for far more than 'creativity and learning' and, in my experience with kids, the majority of use is mindless. Kids get hooked on games.
Nothing in here is definitive. I am not saying that negative effects of screen time are proven beyond the shadow of a doubt. Personally, what I care about is what's most likely to be true, so I can act on that for the sake of my son. I think it is more likely than not that >2 hours of screen time per day is a negative factor. I think it is more likely than not that reading is a positive factor. I'm not going to wait for something to be 99.99% proven before I act on the information.
[1]http://www.npr.org/blogs/ed/2014/08/28/343735856/kids-and-sc...
[2]http://www.parents.com/fun/entertainment/books/the-brainy-be...
At least based on my kids (4 and 7) I concur. We give them an hour a day of screen time.