I think the crescents are still a an active pack in the bayou but being that hope is to young to become alpha,and also not to mention she still has school to worry about they probably are just lying low as usual

Also who knows there’s a possibility that Keelin is acting as a temporary alpha being that she is a direct descendant from the Seven Original Werewolf Packs

I have already started this discussion before. Crescent Wolf survived the attacks in the season of Originals 5. Julie Plec said in an interview that the Legacies season 1 will answer questions about the Crescent Pack. I think that because Hope talks about them in the past tense, it's because pack has been resolved. Probably the point is that Hope didn't want to be Alpha because she felt as threat to others.

I personally would like to see what @Marcus Labonair said that Keelin is temporary alpha and one day Hope would step up into Alpha role.

About quote from Legacies 1x13, Crescents even after death of theirs alphas, have their abilities. Unification Ceremony works that way for centuries. Alphas died but they abilities remain in pack that's why after the centuries all Werewolves have the same abilites.

Hope's recipe is probably used to choose one of their minds after transformation. Because Crescents have access to both sides of their mind this is probably dangerous (Emma said that division between minds is important) and they created this elixir to help. I don't really understand why this elixir and turning at will are connected. For me better explanation would be if this recipe was created when Crescents were cursed via Crescent Curse. This would perfectly explain why they have that much control and averence in wolf form.