The reason RPC is making a comeback is because of 1. SSR (e.g. rendering React components to HTML on the server-side), and 2. the increased practice of continuous deployment.

Increasingly, the frontend is deployed hand-in-hand with the backend.

RPC is a match made in heaven for stacks where backend and frontend are deployed in-sync.

There really are only two reasons for using a RESTful/GraphQL API: providing third parties access to your data (e.g. Facebook API) or decoupling frontend and backend (e.g. Netflix uses a loosely coupled microservice architecture).

Most projects don't need either.