If you compare Thailand (never colonized) with India pre-independence, they look about neck-and-neck in terms of development. At a glance, it seems Britain "looted" India to about the same degree that the Thai monarchy "looted" Thailand.
https://ourworldindata.org/grapher/augmented-human-developme...
Sure, the British aristocratic class did exploit the working class. But then we're no longer talking about geographies.
So why was India's development status comparable to Thailand in that case?
"A good counterpoint to Thailand is Britain becoming insanely wealthy by contemporary standard during Victorian era."
Britain was the first country to industrialize. Switzerland and the US also industrialized early, and did not have a massive colonial population to exploit. But you can see their per-capita GDP was still in the same neighborhood as the UK in the late 1800s:
https://ourworldindata.org/grapher/gdp-per-capita-maddison-p...
A lot of stories that Indians tell about their history fall apart when you look at the data. You can argue that Britain delayed India's industrialization, but since most of Asia was not industrializing at the time, it's a bit of a dubious argument. I have little doubt that Britain exploited India, but I don't think it was a historically exceptional type of exploitation.
A debate does exist around the how much of India's decline can be attributed to the British as fragmentation of central political authority started long before British arrival.
US and Switzerland had their respective advantages like large domestic market and high value industries. The population of these nations had the time to learn and adapt. The familiarity to western education obviously helped as transferring IP was relatively easy. These opportunities were absent in company ruled India(things did improve marginally once the crown took over). I would largely agree British colonial rule was not exceptional when compared to other mercantile colonies. But I do not see the similarities to Mughal rule of India where the wealth stayed in-house and was even invested locally, the key difference being assimilation vs extraction.
I don't think comparing an already declined India to Thai is a fair comparison.
See https://ourworldindata.org/grapher/gdp-maddison-project-data...
Based on the Maddison Project data, it looks like India's economy never had a huge shrinking event. It was just outgrown by other economies.
In 1700 India was by far the world's most populous country (using modern borders): https://ourworldindata.org/grapher/population?tab=map&time=1...
High population probably explains India's high GDP share in 1700.
Before getting absorbed by East India company, some native kingdoms/empites did start with modernizing their military which indicates there would be a strong effort towards industrialization if it weren't for the British regulations.
India was always populous, so that was a constant.
You may also like to read about increasing famines in British controlled regions, how food crops were forcibly replaced with cash crops and so on. E.g. https://www.researchgate.net/publication/394628864_An_analys...
Unfortunately not many people understand or appreciate how colonialism destroys a country and they just see the end result and claim that the citizens of the country were incapable of developing by their own.
Not only economical, but also psychological (as in lose of self confidence) and cultural (assuming own culture is somehow inferior to the rulers) destruction happens. It is not much different from abused people losing self confidence and blaming themselves and additionallyhaving to suffer victim blaming from others - just at a nation scale.