> Sqlite is great but it is a poor substitute for a "real" database

This is true, and explicitly acknowledged by the author:

> SQLite does not compete with client/server databases. SQLite competes with fopen().

https://sqlite.org/whentouse.html

If you're deciding between Postgres and SQLite, in most cases you're doing it wrong (there are a few exceptions, such as serving a low-traffic almost-entirely-read dynamic website can be accomplished easily with either). Usually you want to choose between SQLite and "anything else that involves writing directly to the local filesystem".