Crypto-Spinozans [who have largely replaced crypto-Lockeans] claim that final causes are merely a "projection" into nature of our own self-seeking desires. Because we hunger and thirst, we impute purpose to food and water. The water is there in order to quench our thist. But because this is a projection, it is not true. Notice that this is a "just so" story. It seeks to explain a thing by providing an origin myth, in this case that of projection. (Even if this origin story is true, it is simply the genetic falacy: that a statement is true or false because of its origin.)
However, it is not true. Aristotle and Aquinas did not attribute usefulness-to-humans as evidence of final causation. For them, the argument for final causes is that "without them we can make no sense of how efficient causes are possible." If, in the common course of nature, A leads to B, and not to C, D, et al., it can only be due to something in the nature of A which “directs” A specifically toward B . That is, final causation is an objective feature of the natural world, and not an imposition onto the natural world by a supernatural agency. Without such a "tendency-toward-B" on the part of A, the efficient cause of (A->B) makes no sense.
The best argument for final causes is the existence of laws of nature, like E=mc^2 or that a species evolves toward better fitness in a niche. In any case: a common course of nature. A causes the generation of B and not of C or D.