Why couldn't Old Testament believers go to heaven?

Les explains that God declared His righteousness for the remission of sins that are past, and this refers to the Old Testament believer. All through the Old Testament economy, even believers, with the exception of Enoch and Elijah, did not go to heaven when they died. Instead, they went down into paradise, the area called Hades or hell, with a great gulf fixed, as pictured between Abraham and Lazarus and the rich man in torment. Les notes that this explains the creed saying Jesus descended into hell, but He went into the paradise side. Then at His resurrection morning, He took paradise to heaven. So now Paul tells us that to be absent from the body is present with the Lord, but in the Old Testament it was not that way. They could not go into heaven because there had been no atoning bloodshed. The blood of animals and goats could not take away their sin; it was a stopgap. God made two exceptions, but on the whole the Old Testament believer could not go into heaven.