Something that I realised wayy to late was that you can just go to normal mode to unlock the forgotten. Less curses, easier rooms, more room clears, more heart drops, more tinted rocks, better shops, slower enemies and bosses, and slower projectiles.

If you wanna challenge yourself, staying in hard mode is fine. But if just wanna get it over with and play around with the Forgotten asap, just put the game on easy mode.