The rookies that have played have done so out of necessity. Guys like Rapp and Fuller are the exceptions, not the rule. This is especially true since they are not drafting guys in the first round. Mid and late round players are far less polished than their early-round counterparts. Akers was worked into the rotation and it increased after the injury to Henderson. But RB is traditionally the easiest position for a rookie to play. O-line, WR, TE, D-front 7, CB are all extremely technique-heavy in the NFL making the play of rookies problematic. Also, because most rookies aren't in NFL shape, they benefit from acclimating to the speed and the cultural differences, as well as the intense physical training of the NFL. Things slow down for them allowing them to play as they been coached and not thinking their way through plays.
IMO teams that play rookies at skill positions do so out of necessity. Just compare the play of the Rams o-line rookies from 2019 to2020. They played out of necessity in 2019 and their performance was inconsistent most of the year but began to improve towards the end of the year. Now contrast that with 2020 with the same personnel the o-line performance was night and day.
Hopkins was a 4th round pick for a reason. The reason being his game lacked the necessary polish to be successful in the NFL. A redshirt year allowed him to work on his route running, to be a more consistent receiver in terms of his physical strength and reception and blocking technique. With Everett ahead of him there was not the need to play him. He had 2 offensive snaps and 50 STs snaps (i.e. pretty normal). It was clear from the moment he was drafted that he was Gerald's replacement.
Personally, I think he will be fine. My only concern will be his drops.