You really have not read up on Indian history isn't it? Let me help you out.
Spices were in demand in world over, always have been. The ability to improve the tastes of meat and preserving food over long periods were a distinct advantage which some societies possessed over others. That's why there was a scramble for them especially in medieval Europe after the Black death and also owing to the fuedatary states there and necessity to sustain populations. Read up on the European history atleast before coming over to these questions.
https://yaleglobal.yale.edu/content/spices-how-search-flavors-influenced-our-world
https://www.livescience.com/7495-spice-trade-changed-world.html
Silk was the main source of trade in China but it had also spread out, so no China itself didn't have the monopoly on them, not even on the famous silk route where Iran and Central Asia was also involved in that. Plus Silk was the fabric of choice for the rich, other fabrics like wool, cotton,fibres etc were still highly in demand. Textile are not even just about the material lol. There is the scope of dying, embroidery, finishing etc associated to them and Indian textile was in fine demand for the finished products we were capable of producing. Please read up on this in detail before passing uneducated judgements that Indians didn't trade anything. Just browsing through the internet will aid you. Check out some links below
http://char.txa.cornell.edu/IndianTex.htm
https://www.metmuseum.org/toah/hd/intx/hd_intx.htm
Silk road didn't just pass through the fringes of Subcontinent, it was a major part of it. It just wasn't a land system, maritime trade network was very deep as well. Even the land network passed through the heart of Indian subcontinent. The southern Indian ports were deeply involved in it. Read up on the accounts of Marco Polo, the man who coined the term Silk Road on his arrival on the shores of South India.
Plus it's laughable of you to say that Indian rulers didn't export anything. Major goods were meant for consumption as well apart from luxury items which were also part of exports. Seriously you need to build up your knowledge base on world history seeing as you are commenting on it. If you are really interested in the topic go through some very detailed books on them
https://www.goodreads.com/book/show/185099.A_People_s_History_of_the_World
https://www.amazon.com/Cambridge-Economic-History-India-c-1200-c-1750/dp/0521226929
Adding some further links to read up on Indian trade networks in ancient and medieval times for you to further read up.
https://en.m.wikipedia.org/wiki/Indo-Roman_trade_relations
https://journals.openedition.org/afriques/1752
https://www.researchgate.net/publication/316786210_Indo-Arab_Trade_Relations
https://www.academia.edu/8592644/Indias_Overseas_Trade_in_the_Early_Medieval_Period
https://qz.com/india/1166083/temple...flourishing-tamil-economy-some-800-years-ago/
Comparision with Chinese artifact's is strange because China has been an independent civilization for its entire history (apart from a brief period in WW2 ) leading to better preservation of its past, while the subcontinent has been ravaged by people from all accross leading to severe discontinuities over the ages. People from various cultures have come in plundered the lands leading to so many losses of valuable reservoirs of knowledge and artifact's over the years. These also stopped the growth of real science and technology from the middle ages onwards, something which didn't hinder the Chinese. This led to our subsequent decline and exploitation by the west.
The reality which you must realise is India is in a state right now it doesn't depend on the British aid, it's peanuts compared to the overall economy. As others have said it's for soft diplomacy/power, to build a relationship with India as a rising global power. We hardly depend on them and really no real change will occur if it's gone.