Fact of the matter is, the odds stacked against the possibility of Brandin Cooks becoming a legitimate #1 WR threat in the sense that guys like Julio Jones, Megatron, AJ Green, Fitzgerald, etc are, are taller than Brandin Cooks is.
I'm going to use the same argument that everyone else uses against drafting interior linemen in the 1st round.
Great slot WRs can be found in the mid to late rounds in the draft. That's especially true in this draft which is the deepest its been in a while, especially at the WR position.
Wes Welker - UDFA
Victor Cruz - UDFA
Randall Cobb - Round 2 Pick 64
Danny Amendola - UDFA
Lance Moore - UDFA
Kendall Wright - 1st round pick 20
Cecil Shorts III - 4th round pick 114
Doug Baldwin - UDFA
T.Y. Hilton - 3rd round, pick 92
I think you get the picture now.