Unpopular opinion incoming - but whatever it is, I hope it's been more of a mentor and figurehead role than roving hands-on development. Nintendo first party have been on fire the last couple of years and it doesn't seem co-incidental that it's been since a little of his iron-grip influence has released.
The guy deserves all the respect in the world for his achievements and will always rightly be regarded as a legend. However, any project needs to be lead by someone with the drive and vision for that project. There were too many stories coming out of development where a direction or a mechanic was changed due to his involvement (Star Fox Zero, Paper Mario etc) often leading to a product that didn't feel cohesive in the way the current titles do.
Maybe its Admiral Kirk syndrome where he still wanted to be a Captain and on the front lines. If so, give him a team, a budget and let him create and direct again.