The reboot of the planet's populace into cybernetic humans didn't happen until near the end of Mondas' tenure in the solar system. Eventually it would break free of the orbit it shared with Earth Prime-Time and travel the galaxy until making its destructive return in the 1980s. But before that it would be home for a long line of civilizations found in other TV series but which just don't quite fit into the "history" of Earth Prime-Time.
These would include the realms not only found in 'Game Of Throne', but also in 'BeastMaster', 'Legend Of The Seeker', 'Wizards And Warriors', and even a comedy like 'Krod Maldoon' (although references to Atlantis are troubling), And why not? Earth Prime-Time can be home to 'Secret Agent' as well as 'Get Smart', so why not a goofball thud and blunder "epic"?
I'm still not sure about 'Conan The Barbarian'. I'm tempted to send that off to Mondas as well.
But it wasn't always a world of swords and sorcery. Empires crumbled and new countries were born, and technology advanced so that magic was pushed to the side. There is an episode of 'The Twilight Zone' called "Number Twelve Looks Just Like You" which supposedly took place in the year 2000. Since nothing like it came to pass on Earth Prime-Time a dozen years ago, I've relegated that episode to Mondas as well. (The year 2000 on Mondas is equivalent to the Dawn of Mankind on Earth Prime-Time.) And the replacement of their bodies was a precursor to the replacement of those bodies entirely with cybernetics.
Mondas is long gone, but that isn't an impediment for a Time Lord. So it is still pozz'ble, just pozz'ble for the Eleventh Doctor to have visited the planet and then to sit his Gallifreyan gluteus maximus on the Iron Throne in King's Landing.......
And wouldn't Arya Stark make for a fantastic Companion?