Well, not everybody. But certainly Abraham and Isaac, Elijah and Noah, Ruth and that guy who married her and his mom.
Before Jesus died on the cross for our sins, the gates of Heaven were closed. So all the good people that died before Calvary went to what we call "the Limbo of the Fathers". That must have been a pretty cheery and interesting place. Moses and Aaron, David and Solomon! What a crew!
Then, when Jesus was dead for three days...a day and a half, really...where was He? Opening the Gates of Heaven and the Gates of the Limbo of the Fathers. I figure He had to have opened the Gates of Heaven first or there would have been a bottleneck. Maybe St. Michael the Archangel did it for Him. Since Michael is an angel and not a person, he would have already been living in Heaven with Gabriel, whenever Gabriel was there and not here delivering news and messages.
We mention this incident when we say the "Apostle's Creed". That's what we mean in that part where we say, "He descended into Hell." Technically, we should say, "He descended into the Limbo of the Fathers." I guess they thought that was too wordy.
Everyone who is dead and in Heaven is a saint, and certainly people like Moses and Abraham and David and Noah and his wife are there.
St. Joseph died before Jesus died on the Cross, too. And so did St. John the Baptist. They had a short stay in the Limbo of the Fathers. I guess they aren't really 'before the time of Christ', but they died before the Gates of Heaven were open.
I suppose what you actually want to know is, why aren't these people called "saints" and why aren't they canonized? That's because we didn't start canonizing people until much later in the history of the Church. St. Peter and the Apostles were never canonized. We've only been doing that since the tenth century. Before that saints were named saints by popular demand, and while this seems lovely, too many cookamonga stories were circulating about too many people, some of whom never even existed. So the Church tightened the rules about sainthood and demanded proof. That's why the first thing we do with anyone who is considered for sainthood is dig them up.
I'm not sure why we don't bother to call them saints. Habit, I think. Like Mary. Once in a while we call her St. Mary, but not so much, really. She's just Mary. Like Moses.