Why has it been 10 years since Miyamoto's last new character?

Shigeru Miyamoto recently said that he feels like it’s time for him to come up with a new character. He’d like to tackle this idea when next year rolls around. It seems that Miyamoto came to this realization when he noticed that it was 10 years since Pikmin came out on the GameCube. Apparently, he considers Pikmin’s characters and universe as his last ‘new character’. What has taken this brilliant mind so long to come up with another endearing character or two?