The “atheist worldview” is not the relevant variable, its the scientific one. What “apparent design” does one have in mind here, and what makes it apparent? Its revealing that the questioner gave no examples, meaning this was more of a deck-stacked presupposition.
So let’s speculate on what the questioner may have hand in mind. If we take the “throughout the universe” part seriously, since the only life we know of is here, the rest of the universe is just stars and apparently lots of planets. Do any of those appear to be “designed”? Not that I know of, nor do we find even design advocates going out of their way to point to some weirdly located gas giant orbiting a small star as a herald of divine planet making.
There are the claimed “fine tuning” aspects of the fundamental physical constants that design advocates wish to see as intentional, but as we only have the one universe to look at, we really don’t know any of those constants can be anything other than what they are, any more than 1+1=2 is just an option. True, if 1+1 can equal 3 or 5 or 9 (and maybe all at once), then you’ll probably find balancing your household accounts considerably more difficult. Maybe 1+1 can only equal 2. And energy will always equal mass times the speed of light squared, and the speed of light won’t change either.
So by “apparent design” are they actually meaning biological systems? Well there too the quest for design is more a matter of what all you want to leave out, until it can appear to be intentional, because leaving in all of the data makes the proposed intentions seem rather odd.
Take our own genome. I often hear from creationists the Intelligent Design trope that our DNA embodies “information” and information comes only from Intelligence. QED DNA was designed. But these same advocates seem really reluctant to apply that notion to actual DNA, and what we can observe actually happens to it. Some 10 percent of our genome consists of just the “Alu” retrotransposon, a short string of RNA that carries a bit that signals “copy me” to the cell. Which it does, brainlessly, automatically, such that we have over a million of them littering up the genome. Normally they don’t do anything because they lack a “read me” signal (all that stuff is simply whether or not they have a particular sequence of triplets in the sequence that sparks the copy or read processes). But now and then natural mutations can change the tail into a “read me” sequence, at which point that Alu segment gets added into a functional gene. Usually this is not good, causing misfolded proteins and such, but now and then, by the mere luck of the draw, some of those accidentally activated Alus actually improve what’s going on, and that means a selection pressure for their retention.
So, the design advocate would need to explain whether any of the clog of mutating Alus contain the same or different “information”, and if any of them were intentionally design to be where they are and do what they do, good or bad. The same creationists who are happy to invoke “design” as an abstraction get awfully mum when it comes to accounting for the details of what was purportedly designed. What’s wrong with this picture?
Now some branches of this argument prefer to jump back beyond mutating Alus to suggest there MUST have been Intelligence in the origin of life itself, the first replicating cells. Gee, the designer makes bacteria. But what then? It looks like the rest is all that natural variation stuff, and the literally billions of years of slow going betwixt the first life and even the origination of photosynthetic cyanobacteria (which in turn produced the chloroplast organelles residing in the cells of plants) brings us smack dab into the realm of natural evolution, not “apparent design.”
For those who want to see “design” in whatever it is they want to see design in, fine, if that makes them feel better. But for those of us not requiring that training wheel aside, it looks like the vast majority of things in life and the universe are the result of natural processes. No meddling.
And of course that’s quite separate from whether any particular traditional designer is likely as the cause of whatever’s on the edges. None of the religious versions of things seemed particularly insightful in describing the facts of nature, other than the most obvious of things (like animals mate or birds fly). Nothing about the vast expanse or age of the universe, in which our planet originated only after a tag team of supernovae to produce the heavier elements ours has. Nothing about how the first life consisted only of microscopic bacteria, that are still among us, but that it would take billions of years before multicellular life arrived, and even then there were long detours into now-extinct forms (including 150 million years of dinosaurs).
Multiple designers? Ones who fawned over theropods just as prior ones really loved making trilobites?
Maybe. But that model seems ad hoc and unnecessary to me at least, but no more ad hoc than the single designer some advocates seem committed to for reasons other than their study of nebulae or trilobite carapaces.