Whoever wrote that was probably referring to “invincible ignorance”. You can read about it in the Catechism (1790-1794). It does not apply to the vast majority of people. It’s for cases where someone is never exposed to the faith or incapable of understanding it during their earthly life. For example, babies are invincibly ignorant because they have not developed enough to be able to understand the faith. In adults, a common example is the native people that live in such remote areas they may never encounter a Christian in their life. It also applies to people with severe mental illness. Since they cannot know right and wrong, God does not hold it against them. These examples are clear, but for other situations, only God knows what’s in the person’s heart. Only he knows if they are at fault for not believing.
As for why it is better to get into heaven as a Catholic following Church teachings and God’s commandments than to get in through ignorance, we believe in the merits of good deeds. Jesus said everyone will be paid according their deeds. Bad deeds result in punishment after death (if not forgiven and done penance for on earth). Good deeds will result in rewards after death in heaven. What those rewards will actually be is not really described in the Bible, but some saints have written about this.
St. Therese of Lisieux referred to it has people have differing “glory” in heaven and yet having no envy for others in heaven despite their different amounts of glory. Think of a large pale and a tiny glass. These represent two people’s capacity to love God. Even though they are different sizes, God’s love still fills them up completely, so no matter what, everyone is happy in heaven even the lowliest. The greater the capacity to love God, the greater the happiness and joy the person will experience in heaven.
Think about how we love different people to different degrees. We have some baseline amount of love towards strangers, more love towards friends, and even more love towards a spouse. The greater the love, the more happiness and joy it brings. In other words, in heaven those that have led heroic lives will experience more happiness and joy than those that just barely got into heaven. This is why we want to be Catholic. Even if others can get into heaven outside the Church, we Catholics have so much more potential to experience and reciprocate God’s love in heaven.