Definitely not too old!!
I started in the fall of last year at the age of 41 and was competing in rhythm (full bronze) at a major competition after 4 months of weekly private lessons.
I am very motived so I did a couple of 3 dance championships during the year (and placed in both of them!). I am now working on silver rhythm and just started bronze International Latin and Standard. This to say that not only is 42 not too late to learn to dance socially, it's also not too late to train for competitions and to become a competent dancer!!
Best of luck to you!