The Adcock-McDonald line has been drawn a few times. As you alluded to, there were more players than just McDonald involved though, so I don't think this is quite the 'crisis' that some people seem to be hoping for.
Reckon that perhaps Adcock hasn't offered the kind of leadership expected of a senior player, let alone that of an ex-captain. So if indeed Adcock regressed in this area, letting him go is no loss.
I must say that there does seem to be a generational disconnect between he and the playing group. Adcock the senior family man is not one of the boys, such as Browny always was. Not saying it is necessary to be one of the boys, but perhaps Jed's not too strong on connection and empathy, or being the kind of leader (captaincy aside) the club feels it needs. So then he is being judged on his playing ability, and going forward we have players coming up to fill his role.
Sad to see him go, but the time has come.