Neil Brock said:
If your team is very good, you may struggle to find 4.5/5 star potential players. Bear in mind all star ratings are relative to the strength of your squad, the highest level competition you're competing in (ie Champs League, Europa League) and the strength of your domestic league.
In other words, if you've got a 180-190CA player in your squad, it would be impossible to find a 'better' potential player than that one. You may find 3-4 star potential players are actually the best Newgens available.
Also remember the younger the player, the less accurate your scout will be. It's only as they age does their CA/PA ability become more accurate for even a top level scout.