Yup, the succubi were there for people that wanted quicker scenes. They're not girls tied to the main quest.
The girls who affect the main progression are Sokah and Enrie so far
I see. That's something we missed. It should be in the Oter Haven's Quests.
It doesn't affect the main quests. It only affects the brothel-related elements.
Answer: You can safely skip the Succubi and not affect the other storylines. One unreleased side character might be impacted, but now that we know there might be players like you, we'll work around it.