Originally Posted by SeanMcQ:
“I loved this ep but the whole time travel thing annoys me. The tree thing died, lots of people were killed, his planet was destroyed....can't he just time travel back to before all this stuff happened? Save everyone on the station and save his world. Badabing, badaboom!”
Part of the fundamental ethos of Dr Who is about the responsibility of the powerful. Time Lords have extreme power and to change events arbitrarily on personal preference could lead to disaster. Most of the Time Lords were shown withdrawing pretty much entirely from relations with other species. On occaision they did try to intervene in a high-handed way and it normally ended badly. The Doctor and The Master are the only consistent exceptions. The Master doesn't give a toss but The Doctor always tries to keep within the rules (more or less).
As for the Earth being destroyed, that was no sadness. Like Casandra, it was being kept alive beyond its natural time for no good reason. It had long been uninhabited and people had found other places to live.
What is more interesting is how it is possible to destroy the Time Lords. As they travel backwards and forwards in time it is not enough to destroy Galifrey at a certain point in time as that would leave large numbers of Time Lords still existing in the past and able to move into the future. For The Doctor to be the sole surviving Time Lord something truely bizzare would have to have happened to erase the Time Lords from history and something equally bizzare would have to happen to save The Doctor.
It seems likely to me that the Time Lords were the archetects of their own destruction. Firstly, only they have the power to piss about with time and the hubris to cock it up. Secondly, there is indication of internal division. When The Doctor was trying to reason with the Nestine Conciousness he argued that he had tried to help during "the war" but the Conciousness became incredibly hostile once it recognised him as a Time Lord. This would imply that not all the Time Lords were on the same side as The Doctor.