Unfortunately JPII isn’t very clear about what he means. There is a lot of dithering in his answers.
Plainly put:
You can’t get into Heaven without being a Catholic.
You might ask well, who is a Catholic?
Answer: Someone who is:
Validy Baptized and free from sin either through confession or an act of perfect contrition after baptism or someone who maintains the innocence of Baptism.
Q: How does someone become a Catholic?
A: God provides sufficient grace to all to become a Catholic.
Q: How is this grace provided?
Through the visible Church, through it’s sacraments, through the parents, godparents and work of the Holy Ghost through others.
Q: What about those who are ignorant?
A: God will provide for them sufficiently. St. Thomas teaches that if necessary, God will send an Angel to instruct them.
Q: How can this happen?
A: The Church teaches and professes that miracles occur as well as Infused knowledge, bi-location, apparitions, angelic actions. Any of these things can occur without someone humanly speaking be aware of them.
I think that is as simple and straightforward and orthodox an answer that can be provided.
But don’t forget Our Lord’s warning and the consistent teaching of the Church: Not many make it.
From Luke chapter 13: (emphasis mine, notes from douay rheims online)
And a certain man said to him: Lord, are they few that are saved? But he said to them: 24 Strive to enter by the narrow gate;
for many, I say to you, shall seek to enter,** and shall not be able**. 25 But when the master of the house shall be gone in, and shall shut the door, you shall begin to stand without, and knock at the door, saying: Lord, open to us. And he answering, shall say to you: I know you not, whence you are.
Commentary:
*24 “Shall seek”… Shall desire to be saved; but for want of taking sufficient pains, and being thoroughly in earnest, shall not attain to it. *
26 Then you shall begin to say: We have eaten and drunk in thy presence, and thou hast taught in our streets. 27 And he shall say to you: I know you not, whence you are: depart from me, all ye workers of iniquity. 28 There shall be weeping and gnashing of teeth, when you shall see Abraham and Isaac and Jacob, and all the prophets, in the kingdom of God, and you yourselves thrust out. 29 And there shall come from the east and the west, and the north and the south; and shall sit down in the kingdom of God. 30 And behold, they are last that shall be first; and they are first that shall be last.