REST vs GraphQL
While the great REST vs GraphQL debate is still ongoing the entire point of a proxy is that you don't have to decide on one or the other. You can keep using REST on your backend and still use the advantages of GraphQL. This lets you find out the benefits yourself before you make the decision to switch over (or not, you can always keep using the proxy!) All it requires is mapping and matching the types and fields of your GraphQL schema with the REST API arguments. Afterwards all it requires is maintenance and eventual updates for new arguments and it will also function as preparation for the eventual migration. Instead of wondering about REST vs GraphQL go for combining REST + GraphQL.