I wouldn’t see it as a replacement.
SQLite and DuckDB solve different problems and actually complement each other quite well. SQLite is excellent for transactional workloads (OLTP), while DuckDB shines for analytical workloads (OLAP), especially time-series data and aggregations.
We’ve been using both side-by-side in an open-source project for about two years: SQLite for configuration and transactional data, DuckDB for historical sensor data and analytics. So far, it’s been a very good combination.
You can even use DuckDB to query SQLite :^)
DuckDB kind of created this false comparison by their own early positioning, but I've tried to charitably interpret it as modeling the spirit and motivations of SQLite, not literally being "the SQLite for Analytics". Aside from both being in-process databases they are very different.