At least until people - in a couple of years - figure out that the "Postgres for everything" fad was just as much of a bad idea as "MongoDB for everything" and "Put Redis into everything".

It's not "Postgres for everything", it's "Postgres by default". Nobody is saying you should replace your billion-message-per-second Kafka cluster (or whatever) with Postgres, but plenty of people are saying "don't start with a Kafka cluster when you have two messages a day", which is a much better idea than "MongoDB by default".