Unfortunately for many database workloads you are overestimating the relative cost of this factor.
> even if the SQLite query engine is slightly less efficient than PostgreSQL
And this is absurd - the postgresql query engine isn't just "slightly" more efficient. It is tremendously more sophisticated. People using a SQL datastore as a glorified key-value store are not going to notice - which seems to be a large percentage of the sqlite install base. It's not really a fair comparison.
> but SQLite is a strange beast that needs a special diet to perform best.
I don’t see what is strange about it - for large datasets it’s the same complexity issues as anywhere else.
Not sure specifically what your comment is trying to add, since I acknowledged the type of use case SQLite excels in - those where roundtripping are a dominating cost and “k-v” stores, ie simple queries. My entire point is that those are a common but still niche use case.