I never said it's "lite". I can say for certain that in my experience, when writes start to go up, such as stock market event stream coming in, sqlite3 doesn't perform as well as postgres, and scaling writes is hard in sqlite3. But I have no issue scaling Postgres for those data.

If you say, sqlite3 is good enough for most webapps, then I probably agree. But I would not use it for a lot of things that I use Postgres for such as pubsub, or really high transaction rate.