I don't think that the theory of evolution (which I accept) provides anything like the kind of meaning that existentialists such as Camus have in mind. What is the meaning of existence according to evolutionary theory? The only remotely plausible answer I can think of is this: "To pass on one's genes to posterity, since that's what counts as success from the perspective of natural selection." But, of course, natural selection has no perspective, point of view, intentions, or goals. It's a mindless process. So that answer depends on a false presupposition.
Even if that weren't true, it's highly implausible anyway that passing on one's genes could really be the meaning (or purpose) of existence. If it were, then anyone would be missing the point of existence who didn't make it his/her top priority to reproduce as often as possible, to clone his/her genome again and again, etc. But, on the contrary, someone who tried to live such a life would be pathetic.
Evolutionary theory explains how species arise and how they vanish. I'm not sure that counts as providing "a logical structural pattern" to existence. But even if it does, I think the existentialists are concerned about the particular problems that arise for reflective, self-conscious beings such as us, problems that would remain even if existence, as such, had a logical pattern.