there is a difference between concurrency in a distributed environment and concurrency on a single machine across processes. SQLite is incredibly useful for the latter.
not really true, SQLite supports WAL mode which allows concurrent writes (technically write _attempts_, but these writes are exceptionally fast and are serialized to the file-system anyway, so functionally equivalent to concurrent writes for p50 use case).
also, use-case for massively concurrent writes is pretty narrow, and SQLite is not optimizing for that anyway.