Nonsense. You can go tell Meb Keflezghi, winner of both the Boston and New York marathon, that he's not built to run. He's a prime example of a heel striker [1], though slightly less prominent in his later years.
More generally, in [2], a study of elite level runners in the half marathon, found that at the 15km point the top 50 was comprised of 62% rear-foot strikers, 36% mid-foot, and 2.0% fore-foot strikers.
If a certain running style works for you, i.e. you've been running injury-free, don't try to change it. You are more likely to do harm than good.
[1] https://runblogger.com/2011/11/meb-keflezighis-running-from-...
[2] http://journals.lww.com/nsca-jscr/abstract/2007/08000/foot_s...
