So here’s the problem with your approach. You’re taking the dogma and pitting it against the rest of the Magisterium, when you should be harmonizing them. This includes Scripture and all other Magisterial sources, including the 1997 Catechism. The reason we don’t know is because Scripture itself is very clear that God desires the salvation of all and wishes none to perish and yet Christ himself made clear the absolute necessity of baptism.Or other teachings by saints and popes alike.
This makes it clear to us that yes, Baptism is absolutely necessary. Original sin cannot be in the Beatific Vision. But, given what God has revealed of himself, it allows us to hope that there are extrasacramental means by which original sin can be remitted in the absence of personal sin. However, God stopped short of revealing what that is, or even if he has provided any such means.
Now if we are to just accept hands down that God automatically condemns such souls to hell, then we might as well accept Calvinism, because that’s exactly what it would imply: God predestined them to hell without any consideration of their free response to his grace. That outright denies Scripture, it is completely unbiblical. But at the same time, we cannot also just say they automatically go to heaven, otherwise, Jesus’ words would have no real force.
So we have two truths that need to be reconciled: the universal desire for salvation, and the necessity of baptism. What he did not provide us is the means to reconcile these two truths. All God provided us is a little sliver of hope, but nothing definite.
Limbo is not a solution either. There are only four Last Things: death, judgment, heaven and hell. Those who espouse Limbo are in fact admitting, if unknowingly, that such souls still go to hell. Limbo means rim, and it’s not a third state: it is the rim, or the outer edge of hell where the pains are at their lightest and the souls are in a state of natural joy (lightest does not mean nonexistent, because they are deprived of the Beatific Vision).
This is why you have to read Ott’s treatment because he provides the reasoning behind the Catechism’s teaching.