Well, whether one is a Catholic or not, Truth exists. Right? And it has to be absolute Truth because there can’t be truth that is one thing for one person and completely different for another person, because something cannot simultaneously be X and not-X.
Now Truth exists. We can know Truth, or not know Truth.
Since Truth is an absolute, we cannot fully know it except as the absolute; IOW, we take it ‘on faith’ but we have right reason and use that to confirm what we know and can measure empirically.
Empirically we have evidence of Truth that is given by God Himself through Scripture, Tradition, and the Magesterium and guarded by the Church, led by the Holy Spirit.
That’s why Christians, and especially Catholics, can know the Truth of God, of the Four Last Things which are Death, Judgment, Heaven, and Hell, and can know both our purpose for life on earth and in eternity and that this is through knowing, loving, and serving God with all our heart, soul, mind, and strength, and loving our neighbor as ourself.
So we aren’t slaves to a purely material world, rootless and purposeless, living without any true and eternal knowledge, without any kind of guidance or help.
Now if no human being had even lived, died, and returned to tell us that heaven and hell truly existed, that God truly existed, and that we were absolutely and totally free to accept his gift of eternity in heaven, you could make your argument that ‘nobody knows what happens.’
But we DO have a Man who lived, died, rose again, and who gave us the knowledge, the Truth, of what lies ahead and why and how to gain eternal life in Heaven.
So don’t say, “nobody knows’. We know. We have a Witness.