Species go extinct all the time, there are always very unadaptable species around and most of them go extinct pretty soon after they become unadaptable because environments change all the time in the grander scale of things.
An adaptable organism might stay around for longer - or it might be outcompeted in the short term by less adaptable organisms.
Sure, “survival of the fittest” in the short term is obvious, but it’s hardly worth pointing out.