The “unsaints” have not been redeemed, their salvation is not due to Christ, their sins are still unremitted, and they receive no grace. Yet, they are taken to Heaven because there is no other place to put them.
That's the problem with ignore Limbo.
It's difficult to accept that God would condemn to eternal torment an unbaptized babies or someone what followed the natural law written in their consciences but they didn't have the chance to know God and the Church, for example virtuous Americans before the arrival of the Europeans. But if we accept that unbaptized babies and virtuous pagans who didn't have the opportunity to know God would be in a place where, although they don't have perfect happiness because they don't have beatific vision, they have a kind of natural happiness, it's different.