It's not a knock against Watkins. By all accounts, he's super talented. But as you saw last year, EJ was incapable of making those safe, easy throws you speak of. His screen passes were atrocious.
I just don't think teams like the Bills should be giving up future first round draft picks unless its for a potential franchise QB. Sammy Watkins was not the difference between 6-10 and 10-6 last year. Our receiving group was actually good already.