>We must posit that there is something which is, unlike everything else observed, an uncaused cause.

Why so ? there is another alternative: that a cause is its own cause. This is like in some programming languages where everything is an object, classes are just objects whose classes are metaclasses, and those metaclasses are just objects whose classes are... themselves. So God might be created, its creator is just (possibly another version of) itself.

It's at this point that you realize that our human logics and brains, developed in a universe where (apparently, who knows how the sub-quantum things work) every cause is caused, is entirely inadequate to speculate about the origins of such a universe. If the universe is oftentimes weird, much much weirder than you can possibly imagine, even after you adjust for its weirdness a thousand times over, if its phenomena and patterns often defy our brains and make us invent a myriad myth and superstition to account for them, what can possibly compel you to believe that that which is beyond the universe is even comprehensible, even in principle ? that it can be even hypothesized about and queried by our language ?

>Various other arguments show that there can only be one uncaused cause

I'm not aware of convincing arguments for the necessary oneness of a hypothesized supreme being. The one often employed by the followers of the religion I was born into is an appeal to the "Conflict-Free Universe": Assume there are multiple equally-powerful supreme beings of independent wills, then they will necessarily clash, and that will manifest as conflict and corruption in our universe, which is obviously ordered and free of all conflict and corruptions, and so it must really be the case that there is but a single will behind this universe.

There are several glaring holes with this kind of reasoning

- It assumes we can recgonize a clash of gods when we see it. Do ants or bacteria recognize when humans have wars or conflicts ? I don't think so. To borrow some religous people own favorite phrase, "Absence of Evidence is not Evidence of Absence". If gods (or supreme causes, or whatever you call it) are invisible, then so are their potential conflicts.

- It imagines gods as humans, or at least animals. Why would several independent wills necessarily leads to infighting ? Mathematicians, for example, do not often fight about the truth of proved theorems, although each one of them is an indepedent will. If the whole of existence (of which our universe is just a small part) is like mathematics, or chess, and all gods have perfect minds capable of grasping it in its entirety, then there will be no conflict, truth will compel all independent wills to agree simply by being so blindingly obvious. If creating humans is the single best possible thing to do, then all gods will agree to creating humans, and furthermore they will even agree about which of them should create them, and what tools or materials they\it should use while doing so. In a game of perfect information whose players are infinitely-powerful computers, there is no need for cooperation, communication or coercion in order to agree on the best strategy, all players will simply compute the same answer independently (while taking each other into account). The above argument implies there is some random or unjustified choice that god is/was making, and thus several gods will necessarily clash with each other.

>such a cause must be infinitely good

I find this a bizarre leap of faith. Why ? why should your idiosyncratic morality, which was probably abhorred and decried as false by generations past, and will be abhorred and decried as false by generations to come, be the mark of an eternal and immutable god? you can no more know the morality of a hypothesized god than you can know the number of arms and legs he has, or whether he is even a he. Indeed, the Problem of Evil presents a very compelling evidence that God's morality, if there is any, can never be grasped or understood as anything but a random entropy source by humans.

>It's philosophically bulletproof

Nothing in philosophy is bulletproof, however convincing it may seem (to you). This is a field where people routinely doubt their own existence before breakfast.

>although for some reason contemporary people act like it's not, I guess because we can build iPhones now

Atheism is older than religion.

>Modern atheism is really disappointing because for the most part it doesn't really grapple with the actual hard questions.

It's kind of a mixed bag really. Evolution, for instance, gives a completely new and horrifying spin on the Problem of Evil, which I believe to be the single most devstating blow against any ideology that believes in an inherent good in the universe, and is the cause of me abandoning my religion. On the other hands, new atheism often focus on annoying and besides-the-point things, like God's views on homosexuality or irrelevant scientific errors in holy books. This is useful to show how similar are the holy books to the views of the time they were written in (which, in turn, makes one suspicious as to how an eternal and transcendent god can be affected by the vulgarities of the time), but leaves multiple escape hatches and holes for the opposite side to squirm through. Ultimately, the failing of central atheism is not something it believes, but something that all modern popular ideologies struggle with: the rage-inducing and shallowfication effects of modern media.