You are right that the knee jerking with Keane is unhelpful. I probably share the view that many have on here he will never be a top centre half as he's just not comfortable enough high up the pitch. The caveat to that though is we are a long long way off being a top team. His type of defending, winning tackles, headers, blocks etc will do for the foreseeable period.
We need to remember Moyes kept Stubbs and Weir for the bets part of 3-4 years on taking over. Neither would have gotten into his later teams, but provided a stable base for us to work from. Thats how I see Keane.
I also think he has improved a fair amount this season. You don't become a different player but what you can do is improve on your strengths.
He's had 2 years here now and I think he will improve further in his third year and hopefully start showing some leadership. IF/when we ever get to the top 6 then we have a different conversation.