Agreed, my point is that since people could (and still can) run mostly fine on MyISAM and MongoDB despite their lack of real concurrency, then SQLite in WAL mod

Agreed, my point is that since people could (and still can) run mostly fine on MyISAM and MongoDB despite their lack of real concurrency, then SQLite in WAL mode should not have any problems for a small to medium website. Note: Personally I would pick PostgreSQL any day, unless developing an embedded application.