Agreed. I ran a log ingestion infra 8 years ago doing 20k msg/s sustained on RabbitMQ ... back then we went through a lot of instabilities though they settled over time with new releases. Great times. Besides a quality product the development/release process was very professional and mature.
The biggest issue back then was finding a quality client implementation for the language you were using. Not sure what the status of that is these days.
AMQP and MQTT are both industry standard protocols. Also, RabbitMQ allows you to abuse the limits set by these standards.
Its unfortunate your team ran into performance issues, as Erlang can be inefficient in some situations. Were you using static routes on the DNS load balanced parallel consumers, or relying on the disk caching mechanisms?
The biggest issue back then was finding a quality client implementation for the language you were using. Not sure what the status of that is these days.