An insult like this always says more about the author than it does the target. It’s an easy way for someone to diminish the importance of their own lack of career progress by setting someone else’s success as being based in something that is completely outside the criticizer’s control. It’s like saying “well, I am not a member of X category, so I am not able to partake of the same privileges that they are — therefore, I can dismiss their success as being unearned”. This way they avoid any painful self-evaluation of their own lack of progress in an upward direction. In short, sour grapes.
Anyway, congratulations! Keep going and keep growing. :)