Most often, the main reason to create a new product is that you want it to be different from the existing ones on the market. After all, why waste time and effort to copy the existing solution, if the users, most likely, will choose the 'original' which has already earned recognition in the market?
Similar to any other product, a design system has users. So as with strategy for 'regular' products, it is best to start by understanding these users.
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