Hi!
I'm not too familiar with all Retrofit features, but from what I know there are 3 main differences:
• Retrofit is HTTP only, while kotlinx.rpc is protocol agnostic
• Retrofit is JVM only, kotlinx.rpc supports KMP
• Retrofit uses it's own network engine for parsing requests, while kotlinx.rpc delegates data transportation to a selected library/framework, for example, to Ktor. So that way you can add kotlinx.rpc to your existing Ktor applications with little to no effort