We don’t know if the order is destroyed. Since the films had nothing to say about the other surviving Jedi Rey isn’t alone or the Last Jedi. Although they sort of were saying she was going to be the one who brought it back, and hinting at Finn having force sensitivity. The possibility of him being her apprentice.
Ahsoka might not think she is a Jedi anymore but i doubt she is dead, and Ezra is probably somewhere and they can’t be the only Jedi in a very big Star Wars GFFA.
Point is Luke should’ve been the one to restore the Jedi Order. Not some overpowered, underwritten mystery box entity.