There are arguments from both sides and I see valid points in both.
As a squad player and at 31 years of age he fits a lot of criteria, he is also already ours and we don't need to pay a transfer fee to bring him in. He probably accepts that his place in the pecking order will be low but gets paid pretty well and sees no need to rock that particular boat.
On the other hand, "good enough" is a bit inaccurate in my eyes. Often his first contribution when he comes onto the pitch is to give away 3 or 4 fouls and get booked within minutes of coming on. When you bring on a defensive minded "enforcer" type player thats not what you want, you only need to look at Franco to see how tenacity and aggression can be channelled positively without giving away foul after foul and collecting yellow cards like Ronaldo collects trophies.