They have the more raw talent but not the experience.
Most of them likely do but not all. I know some players who never made AFL but have played in u18 rep sides and made SANFL grade but either were 2 short, lacked work rate or got into too much off field strife so were not even looked at.
One player that was deemed to short iirc (174cm same as Cyril who went that years draft) was basically a better ball winning version of Jaimie Elliott (freak over head high mark but could also play midfield) he played for NSW u18 champs team had games of 35 disposals and kicked 3 goals Loccy Mcgregor.
Not a look in at even a rookie spot and he was a hard working clean skin. Him and Taylor walker played off in the local GF Walker kicked 9 for North Bulldogs and Loccy 10 goals down the other end as 16/17 yo for Central Magpies (basically wear pies kit).
Would regularly take speccys like that on rucks head from pure leap. Plenty of talent in non AFL players and freak athletes that dont get a look in for whatever the reasoning.