Don't think anyone was suggesting Collins get dropped completely from the squad (apologies if there was). The big concern though is that there didn't seem to be viable competition for his place (only his brother) and as such he may have been "resting on the oars" a little bit. Another keeper in actively vying for the position of number 1 number 1 would bring them both to a higher level I think, and ultimately be better for the team.
The fact that if Cork had progressed against Galway, Collins who apart from dropping the lob into his own net (it can happen but hopefully will never ever happen him again in a Cork jersey) was beaten by a shot from the end-line would still be in goal for Cork for the next round because there was no viable alternative was a major concern imho