Did a statement by John Paul II mean only Catholics can be saved?
The short answer
No. His remark matches the Church's constant teaching. He spoke of those who "reject" the Church, meaning a conscious decision against a Church one knows Christ founded.
John Paul II's remark is consistent with what the Church has always taught. In context, his word "reject" means consciously deciding against the Church while knowing it was founded by Jesus Christ.
The Catechism confirms this: those cannot be saved who, knowing that the Catholic Church was founded as necessary by God through Christ, refuse to enter it or remain in it (CCC 846).