Isn't this far exaggerating the problems with Hu Jintao government?
Firstly about pollution, 1-2 years of change wouldn't have meant much. Hu's China was a responsible power in climate that juggled the needs of a well developed industrial sector with the needs of the environment. Under no time did China's per capita pollution rise above the German one, a nation with roughly comparable industrial development.
Under Xi it is not much different.
The Washington tagline based on half truth that China is the "biggest polluter", well, China is the largest developed nation and the largest nation overall. Everything must be examined at a per capita level, if you do arbitrary groupings, I can also say "the West is the biggest polluter in the world", or "western democracies are the biggest polluters in the world". It is expected and normal for China to have the largest consumption as long as the per capita level isn't untenable then
So pollution is just a big nothing burger for both Xi and Hu governments, the only actors trying to make it a big deal are malicious ones.
Xi did further strengthen anti corruption measures but its not like the Hu government didn't have strong rule of law and institutions either. There was a decent level of efficiency, and not much money fell into corruption.
The greatest of the Hu era corrupt official was probably Bo Xilai who gathered 25 million+ RMB through illegal activities. That might sound like a lot but on an institutional level, it's peanuts, skimmed off the top in an unnoticeable way, rather than crippling corruption that destroys whole projects.
Without the effective institutions of Hu, it wouldn't be possible to cast a wide net like Xi did when he reinforced existing institutions either.
So I think the role of Hu shouldn't be discredited, but Xi defintely achieved more than Hu which was not doing much besides keeping the status quo.