Enoch, Abel, Abraham, etc. were saved by what Jesus would do later. In the OT they're called righteous, meaning believers in God. It was through faith then, just as it is now. They didn't know Jesus by name but faith in God saved them through the blood that Jesus would shed later.
Muslims? Bhuddists? John 14:6 Jesus answered, "I am the way and the truth and the life. No-one comes to the Father except through me.

BUT: Jesus also said that whoever knocks, the door will be opened. God's will is that everyone will be saved and he made that possible. We don't know how, but Muslims and the rest can be saved through Jesus.

“In a time of deceit telling the truth is a revolutionary act.”
― George Orwell

It's not over when you lose. It's over when you quit.