Even if he wasn't a mental case and immature, the Rams have no need for him.
Reynolds has proven again and again that he's a starting caliber WR, and whenever he's called upon he shows up. From timely catches to TD's. Clearly Goff and McVay trust him. He knows the offense and the routes and has practiced them for 2 full seasons.
Behind him is Thomas who is stuck behind 4 really good WRs and has a heck of a time getting on the field. But he has the attributes, speed and size to be a contributor and he has been with the Rams ever since McVay, so he knows the offense and the routes.
What the Rams need is better Oline play. Not more WRs.