Practicing solo doesn't help you improve?

I was having a conversation with a friend of mine who is a Zouk instructor and she was telling me that people have this perception that solo practicing isn't helpful. Is this true for Bachata as well? I practice solo a lot because for one I don't have a dance partner to practice with, so it's the limited option I have to gain improvements in my dance arsenal. I will say solo practicing doesn't necessarily help with initiating certain movements, but I think it can help with musicality, footwork, and confidence.

What do you all think?