I'd consider no relational db scales reads vertically better than SQLite. For writes, you can batch them or distribute them to attached dbs. But, either way, you may lose some transaction guarantee.
Reading without write contention is not a terribly difficult problem. You could use any database and it'd work fine. It's the mutations that distinguish db engines. Sqlite is indeed close to ideal but the comparison to other databases (at scale no less) is without substance.
Generally to scale reads appropriately (to >10k readers) you need things like connection pooling and effective replication of some time readable secondaries (which can maintain transaction guarantees if you do synchronous writes, which... maybe not great) - I dont think SQLite has either of those.