Your argument has nothing to do with HTTP and everything to do with synchronous vs asynchronous messaging and request-response vs events. HTTP/2 and WebSockets handle both easily.

Kafka, and its cousin ActiveMQ Artemis are messaging systems best suited for pub-sub events. Both of them are excellent tools for that purpose. Both create complexity over an HTTP-based system but can be justified for higher volumes.

If you are curious about what I mean, you might enjoy reading the following post:

https://medium.com/nerd-for-tech/designing-microservices-4130bc41c046