The cosmological argument

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If I understand correctly, this is the continuation of the cosmological argument:
There is some in the world.
Everything we know has a reason.
There is also a reason for the existence of being.
To avoid getting stuck in an infinite loop, we must assume that at the head of the chain is a cause that is not one of the things we are familiar with.
For the above reason, it is called God.
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I did not fully understand the meaning of this proof. After all, even in the end we must admit that we do not know, since we have not the slightest idea what the unknown thing is that is not subject to the a priori rules of logic that require a cause for everything. What compels us to say that we know what the cause of the universe is, except that this is one of the things that is not known and understood by the mind of the human race, and not simply to say that we do not know how to answer the question of what the cause of the universe is.
Apparently, the answer that the rabbi would give me is that we really don't know how to answer the question of what the cause is, but rather we only define that cause. But then I don't really understand where the argument with atheists is here. I'm pretty sure there are many atheists who don't claim that there is infinite regression here, but simply claim that they don't know. They just object to attributing the cause to God in its familiar meaning. But if God is just the name of the cause, it seems to me that everyone should agree on that. Isn't that right?
(In the physico-theological argument, I can understand that its purpose is to prove that there is some kind of intelligent design here because the other possibility that atheists hold is that there is not. But regarding the cosmological argument, everyone agrees that there is a reason, and everyone agrees that we have no idea what it is, so where is the debate here?)