The Saptarishis were seers. From them the hymns of the Veda effused.
There are four classes of rishis in mythology.
Devarishi is a celestial sage – Narada.
Rajarishi is a wise king (Raja) – Janaka.
Maharishi has not realised Brahman yet – Valmiki.
Brahmarishi has realised Brahman – Vasishtha.
The story of Kaushika/Vishvamitra shows the path to supreme knowledge – Rajarishi – Maharishi – Brahmarishi.