I think it totally depends on what you define as "success."

Is it winning a major champtionship like Blackpool or the Ohio Star Ball? Or at least making it to the top ranks of competitive professional dancing? Then you are starting late. The latest I know of a current champion starting was in his early 20s. To succeed that that level starting at your age, you would need great talent, great dedication, and a lot of time and money to devote to full-time dance training. Even then, the chances are probably not in your favor.

Is it making a living as a dance teacher and having a competitive career? You can certainly do that, but you will probably have to live on a smaller income for the first few years (as you would if, say, you went back to school to learn any other new field).

Is it to become the best dancer you can be? You can start at 90 for that goal. It's never too late to start dancing or to work at being the best you can be.