If Nintendo released Mario Kart or Smash Bros every year, I would stop buying them. One of the many great things about those two franchises is that they only come around once per console cycle. They go all in and make the best possible version they can, every time. You know what you're getting is going to be amazing, and that you'll be playing it for literally years.
Nintendo couldn't possibly, at all, make a full Smash Bros every year. It takes hundreds of people two to three years.
Nintendo is smart. Annualized franchises are horrible.