Fwiw, more recent versions of Druid have a no-rollup mode that does ingestion row-for-row. It ended up being useful for cases where you _do_ care about every row, maybe because you want to retrieve individual rows or maybe because you don't want to define your rollups at ingestion time. And in that mode, Druid behaves like the other DBs you mention.
(I am a Druid committer.)