You better hope you dont have any big indexes or your writes will queue and you start getting "database is locked" errors. Good luck queueing writes properly at the application layer without rebuilding a full distributed queue system / network interface / query retry system on top of SQLite.
I really really really wish SQLite or PGLite supported multiple writers, especially if the queries are not even touching the same tables.
SQLite is designed for application databases.
Postgres is designed for client-server.
It's not about "power" (what does that even mean?), it's about totally different design choices that are intended for different purposes. It's an architecture question, not a "power" or "visitors" question.
Again, huh?
Client-server vs locally embedded does not map to "many bulldozers vs 1 shovel".
SQLite and Postgres aren't even really competitors. They serve extremely different use cases. I'm not aware that "most" people are picking Postgres when they "need" SQLite. What are you even basing this on? SQLite is already an extremely popular choice.
Would you except "Just use postgres for client-server" as a reasonable change?