Familiarity with SQL is a plus in my opinion. Also, DuckDB has SDKs in more languages compared to Polars.
I still love that idea but SQL turns out to be so battle-proven, reliable, flexible, capable, and well-documented that it's really hard to beat. After giving it a shot for a couple of weeks it became clear that it would yield a way more flexible and capable application. I'm confident enough that I can overcome the rough edges with the right abstractions and some polish over time.