In my opinion, and leads non-experts to misinterpret what evolution is.
Firstly 'fittest' has NOTHING to do with being fit, nor was that its intention. It means 'best fit for its environment'. So a weaker individual's genes will prevail if it is a better match for the availability of food, level of competition etc. In fact being stronger/higher stamina is not a key factor at all, otherwise humans, and all animals would be far far stronger/fitter than they are now.
People who despair at the fattening populations, or conclude that evolution has halted on humans might have this misunderstanding.
Secondly, 'survival of the fittest' suggests that a few individuals are better than the rest of the crowd, and they alone proliferate with many offspring. This is misleading, a better phrase would be 'non-survival of the least fittest', which is more accurate in describing evolution.
i.e. it is the worst adapted, or the problematic cases which tend to not reproduce which drives evolution; it is driven from the back more than driven from the front.
This may not sound right, e.g. only 1 sperm of millions makes it to the egg, or only a few frog spawn make it to frogs. But this doesn't mean the few that make it are the 'best', more accurately you would say that the frog spawn that make it to frogs without being eaten are fairly random lucky ones, regardless of their fitness. The only ones which *definitely* won't make it to frogs are the least fittest, which can't swim, same with sperm.
So wouldn't it be better if the phrase we used was "discontinuation of the worst fitting"?