There's a huge gap between League 2 and the SPFL - even in fitness you can see a lot of guys that head north are not fit enough to play.
I think the overall point is being missed though. It's not that a player is useless for 6 months. In this case, for me, Dunne was doing OK when it came to the basics of running, heading and tackling. People were judging him negatively on his ball retention and distribution. Now he's been playing a few months, that has improved. He's also had to learn things like how best to play in a back 3 one week and back 4 the next - and with different players in front of him; some who can defend and others not so much.