The historical pattern I observe is the one to which you alluded. God was once posited as the cause of eclipses, earthquakes, the movement of the stars, origin of humanity, etc. And each time it has turned out there is a sufficient naturalistic explanation. So forgive me if I'm skeptical when someone says, "No, but this time, God really is the cause!"
In terms of capabilities becoming more advanced over time, it's not so much about time itself as the idea that advanced capabilities require more primitive capabilities to build upon. Starting out with advanced capabilities from nowhere seems absurd. Presumably you agree, but only in the context of our universe. And sure, if we throw out all experience, evidence, observations, and anything else we can verify, and posit a realm where anything is possible as long as it's not a logical contradiction, then we can make up whatever we want. But that's an act of imagination, not reason.
For the record, there are several professional philosophers who have written critically about the first cause argument, including Michael Martin, John Mackie, Quentin Smith, Bebe Rundle, Wes Morriston, and Graham Oppy. So I don't think it's been lacking "due attention".
You implied that even if the first cause argument didn't hold up, you wouldn't lower your confidence in God's existence at all. If this is true, I can only conclude that the first cause is irrelevant to your belief in God, and is not one of the actual reasons for that belief. In which case, why should it be convincing to me? And it also begs the questions: What then is the best argument for God's existence and why aren't we discussing that instead?
From where I sit, it seems you are confusing logical necessity (we cannot imagine it being otherwise) with empirical necessity (we can imagine it being otherwise, but in actuality, it can only be one way).
Logical necessity: 2 + 2 = 4
Empirical necessity: One can imagine that either I fathered children or I didn't, but in actuality, only one of those things can be true.
The existence of a first cause is logically necessary. We agree on that.
I say we can imagine the first cause to be X or Y (or Z, etc), but in actuality it can only be one of those things. This is where we appear to disagree, and I'm trying to find the crux of it.
You say the first cause's "existence is wholly independent...that means that it exists no matter what, for its existence is not dependent upon anything." The implied end of your sentence is "...not dependent upon anything in the omniverse." Of course, since the omniverse encompasses everything that exists, it's unnecessary and redundant to say "in the omniverse." But if we are talking about possible, alternative omniverses, then we might imagine Omniverse A and Omniverse B.
Omniverse A: X is the first cause, and its existence is not dependent upon anything in the omniverse.
Omniverse B: Y is the first cause, and its existence is not dependent upon anything in the omniverse.
Now, since there can only be one omniverse (that's the nature of the term), either A or B (or C, etc) has to be the actual omniverse and therefore either X or Y (or Z, etc) has to be the actual first cause. But it doesn't follow that being wholly independent of anything in the actual omniverse means something must exist in all possible omniverses.
Imagine the laws of physics cease to exist. What do you think happens to atoms?
You seem to be basing your argument that an "I" cannot emerge from matter on free will. You may or may not be surprised to learn that I reject the notion of free will. Indeed, I think it is incompatible with the first cause argument itself. The first cause argument establishes quite clearly that everything (except the first cause) must have a cause. So that means any decision a human makes has a cause. And that cause has a cause, and so on. As we follow the causal chain backwards it will eventually precede the human in question's own birth. So in what sense is the decision "free"?
