It is set in M-space. (Mavity, magic) My personal term, but I'm not enforcing copyright.
The Doctor is no longer a Time Lord from the planet Gallifrey in the constellation of Kasterborous. They are from yet another dimension or universe, apparently, and brought back by the first Time traveller. They have unlimited regenerations, and are therefore immortal, but have not succumbed to the ennui of, say, Wowbagger the Infinitely Prolonged. Go look it up.
The logical result of which could be an entire Universe populated by Doctors zipping back and forth through TIme. and no one else, eventually.
(The 12 regenerations and you die physically forever and your mind is put into the Matrix now only applies to Gallifrey-born Time Lords I presume.)