I stopped trying to wrap my head around anything on this show ages ago. I just watch and enjoy. I think the reason Tom was the curator is because we, as fans, wanted to see him again, in some way involved with the show. It was a love letter to us classic fans, and I sure did appreciate it.
Tom was the best Doctor, but he was on a lot of episodes with questionable looking aliens/monsters and special effects. His stories and acting were far better than anything on the new show. If they had the budget and technology of the revived series, no one would even try to claim somehow Tennant was the best Doctor.
Tennant was good. So were ALL the others. There are no bad Doctors. But Tom took it to another level. He WAS the Doctor. He didn't PLAY the Doctor.
Tom is getting old, and walks with a cane. He can't ever be the Doctor again. But he was an embodiment of what the Doctor could be like as a retiree.
It was fantastic.