well, it wasn’t that simple either :)
Their colonies WERE in a better shape - but it depends WHERE.
We can’t compare India to Nigeria or Congo etc. nor to Indo-China.
However one can compare Malaysia to Indonesia or Vietnam.
British controlled Malaysia - the british heavily relied on divide-and-rule, so the Chinese and Indians were given a free hand to develop. Indonesia - the Dutch were purely exploitative. Vietnam is on par in many ways with Malaysia - despite being a larger country.
The Belgian Congo was not even a colony - just a pure “exploit everything as much as we can”. The French African colonies were slightly better - only slightly.
The British hit upon a better idea - DEVELOP the place so that you can extract more money from it. The Brits set up railways so that they could extract wealth faster and more effectively. They set up rule of law to save money and expense on policing. They also gave limited rule, so that they didn’t need to spend a lot on British army etc - the largest army was the british raj army which had indians and even Indian officers
The flaw in Britain using Indians in other colonies is that when the British left the natives wanted the Indians out as well - and that happened in east Africa, and today is a source of friction in Trinidad and Fiji.
The Malaya “emergency” was much less bloody than Vietnam’s “unification”. Other colonizers did set up infrastructure, simply to move resources out; you can see remnants of it all over in Africa.