What isn't subjective? So are your points. You don't know whether they could have extended him to his age 35 season instead of his age 38 one. He will obviously decline as a ballplayer, but they felt compelled to keep him after his prime years because of what he means to the franchise. There's no other explanation.
Also, remember that with the way salaries are inflating in MLB, by the time Pedey starts declining, his salary may be a bargain. Since we play in the AL , he could always spend significant time at DH. As for the idea that a better 2B may appear, we should cross that bridge when we get there considering the usual scarcity of two-way players at the position.