Yes. The only way to salvation is through the redemption of Christ. That is why Christians are desperate to spread this news. No one has to go to hell, all they have to do is accept the sacrifice that Christ made for them and believe.
But outside of that, yes, they are stained with sin and will spend eternity in hell.
Gosh, how nice of Christians to condemn hundreds of millions of souls to eternal damnation for the centuries before their Word spread to the Western Hemisphere.