Yes ... if the content model is planned early. Flat-file systems struggle when everything is treated like one generic post, not when content types are well defined.
Scale comes from structure, not from a database alone. If the site has content types, routes, and data fields that reflect reality, a flat-file stack can scale surprisingly well.
A library can combine articles, FAQs, glossary pages, directory entries, and resources as long as each type has a clear role.
The route map and sitemap generation should be planned alongside the content types, not added after the site is already messy.