The only criticism I've ever heard of Bobby Shearer was from Jim Baxter.
He wasn't happy about Bobby as captain negotiating players' bonuses after a successful season. "He'd come back to the dressing room pleased at getting us all a cutlery set. He was the last man we should have sent up because Bobby would have happily played for Rangers for nothing!"
(Not so much a criticism as a back-handed compliment.)
Bobby Shearer might not be included in a list of the most gifted Rangers players but he would feature high on a list of great captains. Whoever introduced the phrase playing for the jersey could well have had Bobby Shearer in mind.