Being a rishi is different from getting moksha. Let me elaborate using the same metaphor of acting in a drama.
A lot of actors (people) in a drama (samsara, i.e. world) take the drama too seriously, do not like what happens in the scene they act and try to change the script to enhance their role or make it look better. They do not realize that the director (supreme power running the universe) picked characters and scenes based on how one acted before (previous lives) and what suits one. They complain endlessly, not realizing the futility.
When people’s scenes end, they are sent out of the drama room (death). Being used to the drama so much, they want to come back and the director finds another role for them (rebirth).
When their scenes end, some people realize that it is just a drama and not real. They leave without any regret or a desire to come back. They do not act again (no rebirth) and they are free from the drama (moksha).
Some people realize while acting in their scene (when still alive) that it is just a drama and not real (jeevanmukti, liberation while alive). They go through the motions, finish their scene and leave the drama (leave body). They do not act after that (no rebirth) and they are free from the drama.
Now, there are some special people (rishis) who realize that the drama is not real and stop taking it seriously and yet are at the disposal of director *forever*. They never leave the drama and do whatever director wants them to do, without complaining and without any attitude. It is also because they understand the director fully and are in sync with the director.
They are free in the sense that they are not taking the drama seriously like other actors (unliberated people) and yet they have not left the drama (like liberated people)!
For them, there is no difference between Shiva (or Purusha) and Shakti (or Prakriti), i.e. non-dual Self and the field of duality are one and the same for them. They can act in the field of duality using an individualized consciousness and yet not trapped because they are in oneness with the non-dual Self at the same time. Rishis have perfect control over the field of duality, but the word “control” is not in an egoistic sense here. They have no ego. In terms of the metaphor, they are the trusted assistants of the director who are in perfect sync with the director and are fully empowered to do anything they want to do with the drama.
Thus, being a rishi is different from moksha.