i love posgresql, but i would not use it to replace a rabbitmq instance -- one is an RDBMS, the other is a queue/event system.
"oh but psql can pretend to be kafka/rabbitmq!" -- sure, but then you need to add tooling to it, create libraries to handle it, and handle all the edge cases.
with rmq/kafka, there already a bunch of tools to handle the exact case of a queue/event system.