I performed the exact opposite migration at $DAYJOB recently - swapping an internal text-based protocol to HTTP (over a local IPC pipe).
The main benefit was we could suddenly reuse all the codegenerated routers/docs/authentication from the HTTP ecosystem. It significantly simplified/standardised our IPC layer and reduced the "weirdness" in the codebase.
Yep. Unless you're doing thousands of requests per second+, the right RPC protocol is likely just HTTP due to the massive improvement in mature tooling, debugging, etc.
The main benefit was we could suddenly reuse all the codegenerated routers/docs/authentication from the HTTP ecosystem. It significantly simplified/standardised our IPC layer and reduced the "weirdness" in the codebase.