Hey Volstskid, people's opinions vary on who's who and who's not. I've experienced a fair bit or randomness in the games I’ve played. Try players out in deferent positions and if you think they can hack it, regularly getting 7 +, then keep them, if not try a different position. If still no joy then consider selling them
I doubt that anyone would be dead-weight. You may have to invest some time in developing some players though. Remember, not everyone in your squat is meant to be a first team player. If that was the case then you'd have 25 unhappy players, some are only there as a back up and some are up and comming