It definitely seems like the Clone Wars are long gone but I never got the impression that cloning was. It’s a big galaxy, after all (wasn’t Lando supposed to be a clone or something originally?). And “several” planets is only six. Hardly a good sample size.
Anyway, even if it was as extinct as lightsabers and such, what’s to stop Kylo Ren from considering bringing it back? If he already has a lightsaber, why not a clone army?