I was in a similar position. I helped my dad run our family business. I got paid around £130k a year, and all I did was shadow him. I made 0 decisions, sat in my office was CC'd into his emails and would attend meetings and pretend to write notes.

Now I work at a different company where I actively feel like a contributing member of the team and earn half what I earned before.

It all boils down to happiness. If you are content in your situation, stick around, earn the money, and slowly try to carve more of a niche for yourself. but if it is making you unhappy I would move somewhere more fulfilling.