There are still a bunch of them it's just that no one knows that there are more than one. Stargirl is Earth 2. Doom Patrol is like Earth 9 or something. Titans is in its own Earth, maybe Earth 18. Smallville is still around too plus the Batman movie universes are the same I think.
Didn't Steel (formerly Capt. Luthor) state in the beginning he got to Earth Prime due to Crisis. All of the heroes of Earth Prime know of Crisis and everything going back due to J'onn. With the exception of Superman they've all mentioned it.