India also has to dismantle the social systems and institutions set up by the British, which were designed to make people at the top rich, instead of running for the benefit of society.

Dismantling this is hard work, and you cannot simply destroy a bureaucracy without having a replacement ready (or chaos). WWII was good for Europe in some ways, because it massively destroyed the aristocracy and a lot of bureaucracy along with it. It was effectively a reboot of society, backed by a lot of cheap funding.