Catholics teach and believe what Jesus taught… that there is no way to the Father other than through Jesus.
Jesus is the only way one is saved.
There is but One Lord, One Faith, One Baptism
Further… everyone in heaven is Catholic. This is so because at the end of our mortal lives, we will see the Beatific Vision (God), and the fullness of Truth (Jesus) will be before us. All obstacles to belief and understanding will be removed, and we shall make it a reality of One Lord, One Faith, One Baptism. Hence we will all then belong fully to the Body of Christ, which is the Church.
Further, … everyone in hell is Catholic. This is so because… (same as above).
However… for whatever reason one has rejected this Truth (in the mortal life), that person has condemned himself to hell eternally, knowing the Truth of One Lord, One Faith, One Baptism.
How much better to study the Truth and accept it now, than taking a chance to believe at the last moment.
Those outside the Catholic Church have less than the fullness of Truth available to them. Kinda like running on half empty. You might make it, but why not use all the graces which the Lord has made available for all.
The Truth is not something, it is somebody, and His Name is Jesus Christ