While the GP may have been referencing the former, embracing "PostgreSQL for Everything" often prohibits the latter.
I think that the "use Postgres for everything" messaging was a necessity, even if it is overstated. Use it until you can demonstrate it doesn't meet your near term needs. When that happens, shift. It wasn't that many years ago when I'd enter situations where people were knee deep in FAANG level infrastructure when postgres on a relatively small instance would have more than been sufficient. I'd suggest they look at converting to postgres to save money & all the energy they spend maintaining their soup. "It won't scale the way we need it!". Sometimes they were demonstrably wrong. Other times they were half-right, in that the real problems was terrible decisions made at the software layer, leading to a situation that required heavier duty infra. Almost never were they actually right* though.
Might they have been right 5 years later? Perhaps. But I know for a fact that none of the ones I encountered were.
As the old saying goes; just because you can do something doesn't mean you should do it.
> I think that the "use Postgres for everything" messaging was a necessity, even if it is overstated. Use it until you can demonstrate it doesn't meet your near term needs. When that happens, shift.
The problem with this approach is, once "use PostgreSQL for everything" is identified as being no longer be feasible, it has already become an inextricable component underpinning system functionality. Thus making "[w]hen that happens, shift" extremely difficult.
Contrast the above with only using PostgreSQL (or any other RDBMS) to manage data and their relationships, eschewing stored procedures as well, and the "when <insert condition> happens, shift" decision becomes much more feasible to entertain.