I do believe in Hell - gotta believe in it if you believe in Heaven. I also believe when God spoke through Jeremiah about how He would bring us a New Covenant and would forgive our wickedness and recognize our sins no more, He was not telling us a lot of lies. I believe that Jesus died for all our sins and the only requirement to reap eternity with Him is to believe He died on the cross to pay the death penalty of all our sins and all we have to do to redeem that is to go to Him as sinners who realize that we cannot be worthy of our own efforts and to accept that He will make us fully worthy if we acknowledge His sacrifice and accept Him as our Lord and Savior.
Those who were rebuked for having fallen from Grace were still trying to be worthy of their own efforts by trying to do the impossible by following the Law that nobody but Christ could follow in order to help save themselves instead of acknowledging His incredible gift of Love.