I agree.
But except the soteriological issues, there is any limit?
And that God would give a way of Salvation is a issue possible to be achieved by reason?
Considerang that God is Act Pure, that He is Love and want the good for humankind?
I wrote that Paul's limit is "general" because there is no rule or method to accurately quantify the precise limit, as if there was a fixed maximum bound by the human nature, which no man overcomes. We might as well declare that no man can run a three-minute mile. Once upon a time, no one believed a man could run a four minute mile, then the record fell. Yet, it may be the case that lowering the record by appreciable amounts (rather than by a few more seconds or hundredths of a single second) gives a hint as to what that bound might be for as long as the world endures.
Study the religions and philosophies of the world, and you may be able to compile a list of convictions that correlate with a Christian's biblically-informed and broadly definitional theology. Still there are inquires left to be made. But perhaps you might be able to say accurately that men unaided by the Scriptures typically attain no more than a modicum of true natural theology by their scrapings. The most renown philosophers: maybe one of them got two handfuls, as opposed to the one, or the single pinch.
Paul declares how men in their sin
do not like to retain the truth about God. Therefore, before they acknowledge too much, they excuse away some degree of the truth to make room for the more palatable lie. But each man is unique, and each man's perception of God passes through his personal filter and goes past his personal blinders. Hence, I do not think your question has a quantifiable answer.
Men tend to hope there is some allowance with God, that he should overlook sin or discount it, etc. Whether this amounts to anything more than wishful thinking seems unknowable. They do not
know that God may be gracious, but they utilize means such as sacrifices in order to propitiate the god of their imagination. This hardly seems like "salvation" to me.
Men should know God is good. But that he is love? That seems quite grand, and not much to be found (I suppose) in the common religion. If the typical local deity was patterned on the behavior of kings, it is not clear to me that such a being would be thought to love in the true sense; certainly he would not love the enemy, or the servant, or any beneath his kind or level. The Greeks and others held that the gods shared between them affections not bestowed on men and other creatures. Zeus might lust for a human woman to marry or rape her, but this is manifestly treatment of an object of ownership and control.
But, in spite of all the improbability, could the natural man conceive that God is love? Perhaps... but then, what would be the cost of that admission? What attribute of the true God would be dropped (as something must) in order to shape the perception around love? Man apart from covenant can barely hold two truths together, without overwhelming himself. He must sink back into his comfortable and willful and culpable ignorance.