Folks, let get real. If you haven't played in 20 or 30 years or you start playing in your 40s or 50s you can practice your rear end off but if the gift of extraordinary natural talent is not there, you will never be anything but a competant player. Let us not forget that the trumpet is, of course, a very physically demanding instrument and after 50 or so, the body just can't do what it used to. Sure, there are exceptions like Doc, Maynard, and Bud, but deterioration, no matter how slow, begins around this age. Without the knowledge gleaned in years of performance and the experience as to how to compensate for the deterioration, it will likely be impossible to ever achieve anything other than very decent performance. If one had that rare touch of greatness within, it is unlikely it wouldn't have tapped into years earlier.
As others have said, with hard work, one can still become a good player and have fun doing so.