The thing is he is not tiers below the best, he is not world class, but certainly not as bad as you rate him. As for build up and transition, that depends on the manager. Smalling played under LVG, and had no problem in the build up and transition. Also, if Jose does not think he is good enough, then don't play him, yet Jose constantly starts him ahead of others. Jose just does not value it as much as you seem do, or else he would not have played. Also, if you stats don't tell the entire story, but they give a good general idea of a teams strengths and weaknesses. The fact that the same defenders have done well under two very different managers tell that they are not as bad as you believe them to be.
It is the fact that they don't start ahead of Smalling, even though as you suggest he does not offer much in the build up. If Mourinho trusted them, they would play. Mourinho has his favourites, and the ones he trusts always start regardless of form. Of course we can win the league with this defence, City have Stones,Otamendi and Kompany in their defence, and they are no better than what we have. Delph has played as their LB for majority of the season. Only Walker has been a big upgrade for them. Their defense is not better than ours, and they are winning the league easily. Smalling and Jones have both won the league previously, so it is nonsense that they are the reason we are not close to even challenging for the title. Again, our defense is not the problem that is stopping us from winning the league.
No wonder you think the squad was shocking if you consider a squad as only 5 or 6 players. You seem to only count the players that were not good enough as part of the squad, and not the ones that are good enough. Yeah you better stop, repeating hyperbolic nonsense won't make it true. And no matter how much money we throw at the team, we won't win with Jose at the helm with this shit football. Something he seems to know as well, so is getting his excuses out early.