Quote
L.A.Rams
The Rams traded a first-round pick for Cooks. In just about any draft, it is possible to obtain a better receiver than Cooks in later rounds. Cooks is currently the Rams 4th best WR (behind Kupp, Woods, and Reynolds) and probably the 7th best receiver (behind Kupp, Woods, Reynolds, Higbeast, Everett, and Gurley). The time has come for the Rams to give Reynolds more playing time than Cooks.

Cooks is a role player, and was never meant to be a #1 WR. He is a fast deep threat. So you can't replace him with just any good receiver---his replacement has to be a fast deep threat.

It also has nothing to do with where he's ranked v. other WRs. He's there because he fulfills a role. If someone else does not fulfill that role, they are not a real sub for him. So Cooks may be the Rams 4th best receiver, but he is their 1st best and possibly ONLY guy in the deep threat role, and if you get rid of that role, you change the entire offense.