Installing & maintaining a Postgres extension is vastly, vastly simpler than running Elasticsearch and Kafka. Like, how could you even compare these things if you know what you are talking about?
Or maybe you are looking at it from "just swipe your credit card at AWS" perspective, in which case "just use Postgres" articles are for a different audience.
Running a small ES with dual save alongside your relational store is trivial. Kafka I will grant you is a lot to operate, but I would not choose Kafka unless I have a Kafka-shaped problem, and if it looks like that I would never, ever choose Postgres. Equating Kafka with “I need a queue” is a laughable comparison.
Or maybe you are looking at it from "just swipe your credit card at AWS" perspective, in which case "just use Postgres" articles are for a different audience.