Some good points being made here.
I think at the end of the day you'll find there really isn't a black and white answer to success. If a player is good enough, regardless of the club they stay at/go to, they will find their pathway.
Its hard to hang shit on guys who decide to jump clubs considering in the professional game, across every sport, people are breaking contracts, being cut from teams mid season etc. That is what these club guys are aspiring to be, so when the ethics of the 'real world' are like that you can see why loyalty has become less common.
For the record I was always a one club man as both a player and coach.