And Exodites do? Last I checked the Exodites don't feel the touch of Slaanesh precisely because they are Exodites. Even Craftworlds still participated in the debauchery of the Eldar Dominion, the Exodites are the Eldar that abandoned the Dominion and renounced its decadence.
IIRC, the claim that Slaanesh has is over the souls of the entire Eldar species regardless of whether they participated in her formation or not, no matter how distant they were from the Eye of Terror and no matter the relations they had with the Dominion.
It's a narrative claim on their souls since Slaanesh basically ate all of their gods and any concept of an Eldar afterlife / reincarnation got gulped down with their gods, she is now their afterlife.
(That last part might not be canon but I choose to believe it is)
EDIT: The Craftworlders stave off Slaanesh by basically committing their entire psyche to a specific role or purpose for a few years to keep themselves from hyperfixating on a chosen role and losing themselves in the process (The Path System) and use spirit stones to capture their souls so they don't go to Slaanesh.
The Exodites rely upon an equal mix of subsisting with the bare-minimum amount of technology and resources to stay alive in 40k but not grow decadent + creating a world-spirit on their planets to capture their souls instead of a spirit-stone, if they leave the planet and aren't given some way of keeping their souls safe when they die, they get schlorped up.
The Harlequins are different because
their souls go to Cegorach instead of Slaanesh because his claim on them is higher, but Solitaires (Harlequins who act out the role of Slaanesh in their retelling of the Fall and thusly catch her attention) have their souls claimed by Slaanesh (although Cegorach is said to try and contest her claim when possible)
The Deldar basically don't stave off Slaanesh, but instead they kind of 'Top-Up' their leaking souls by feeding off of the pain of others.
To sum it up, the Eldar are
always affected by Slaanesh in some way, to the point that they had to socially re-engineer their entire culture thrice over just to survive (with the Deldar doubling down).