Regarding 'helped unify India as a nation', they are not the first. Referring to
https://www.youtube.com/watch?v=QN41DJLQmPk, India's map looked close to the present day multiple times in the past.
Maurya Empire-284 BCE [1:57]
Delhi Sultanate (Tughlaq)-1345 [8:45]
Mughal Empire-1692 [10:24]
As for 'they also brought manufactured goods back', they exported raw materials from India and imported back finished goods, thereby destroying the local industries in India.
>By the mid-19th century, the Indian economy had been fully transformed into a colonial trade pattern, where its export consisted mainly of agricultural commodities such as foodgrains, and the home charges were met by exporting such commodities, while the imports consisted of manufactured goods, especially cotton textiles and machinery (Siddiqui, 2015c). After the 1880s, the trade imports became more diversified, due to the growing penetration of foreign manufactured goods such as cotton textiles, capital goods, machinery etc. (Siddiqui, 1996) This in turn further undermined the position of the local producers and hastened the decay of indigenous industries and handicrafts.
https://worldfinancialreview.com/the-political-economy-of-fa...
Dr Shashi Tharoor did a nice speech about the British rule in India listing out the damages they did: https://www.youtube.com/watch?v=f7CW7S0zxv4. Text version of this speech available here: https://www.news18.com/news/india/read-shashi-tharoors-full-.... His book on the same topic: https://en.wikipedia.org/wiki/Inglorious_Empire
Then there is the famines. Famines during british rule is estimated to have killed from 20-50 million Indians: https://en.wikipedia.org/wiki/Timeline_of_major_famines_in_I.... Google image search of 'british india famines' should show some photos for those who haven't heard of this before. An article talking about why famines occured: https://worldfinancialreview.com/the-political-economy-of-fa...