Gary Mackay Steven couldn't get a contract with Liverpool, there's a pretty obvious reason for that. He didn't show the ability to play for Liverpool so they let him go. He then found his level a couple of Scotland caps and a bit part player for Celtic but never good enough for a top team.
Anthony Ralston is probably an example of your suggested path. Show's promise as a young player plays a couple of games he is not ready for then go's out on loan to teams with very limited training facilities and uninspiring coaches.
Pretty sure he would have done better going to a decent academy and playing against players of nearer his own age, strength, ability, experience level etc
Might even have become a better right back than Phil Bardsley but then Bardsley did have the advantage of joining Man Utd as an eight year old. Coaches there on merit not just availability and facilities designed to hold more than a few traffic cones and a medicine ball
It's a lot easier to name failures at the top clubs than players who might have done better.