To awaken this hibernating thread...
The real issue seems to be mortality. Or lack thereof. Some of the best stories center around the idea that we are mortal, our time is limited, and so are our accomplishments. So, what we do has weight and meaning, because the clock is running down and ultimately we pass. Whatever we have or have not accomplished is left to future generations to handle.
With Doctor Who, the Timelord ticking clock is extended by a prolonged natural lifespan, and then a total of 12 lifetimes. So... we can get more done in a series with the same "person", but the end ultimately will come.
...until now, when from a practical standpoint, they had to get around the 12 regeneration limit. Since the Doctor is now (and will be) basically immortal, and has survived everything thrown at him/her on a galactic (nay, universal) level, the drama is gone. Writers have tried to make up for it by tragedies with the companions, etc. But since we know that our protagonist will always triumph, always survive, and never really "die", then what story are we trying to tell?