I know that I don't know what criteria that use to select the wide receivers that play, but i do know that route running and ability to catch the ball is only part of the picture. Blocking is also an important part of the job, perhaps more important. Remember this
play against Eastern Michigan a few years ago? (I guarantee you that Blake Poole remembers it.). Think of it this way. There are about 80 offensive plays a game, during which a good wide receiver might average 4 catches. Thus, on the other 76 plays, what is he doing? He's either running a route somewhere, or blocking. Also, I would expect things like knowledge of the playbook, meeting attendance, work ethic, and attitude to play a part in the selection of who plays, and perhaps things such as grades or off-the-field issues.
I don't doubt in the least that the person playing is not always the most talented, but that's because a lot more than talent should go into choosing who should play at WR.