Reading more about the Webway because @drukhariboypussy's response to my Eldar Thoughts post got a thought flowing in my head: the Webway is, in essence, a part of the Immaterium that got cut off from the rest aeons ago by the Old Ones. Either because of HOW they did it or simply because it's a "stagnant" pool compared to the vastness of the Sea of Souls, quite literally an ocean of psychoconductive meta-matter, the Webway is much LESS psychoconductive than the Warp.
Eldar physiology, neurology, psychology, what-have-you, whatever you wanna call it is built to by hypertone in its emotions and its connection to the Immaterium. The Eldar feel everything much more strongly and are biologically set up to be super-empathic to the point of being psycho-conductive themselves. In the Asuryani Craftworlders we see this as integral to the functioning of their society but also manifest in their supremacist view upon other sapient species. If you can literally FEEL the emotions of other beings it serves you decently well to simply demean and view other species as "less than" as a form of social conditioning to limit the amount of empathy you feel for them and therefore how much of their emotions you super-empathically take up.
The Drukhari are known to be much less capable of using psychic abilities. This is 100% partially because they are raised in a culture that doesn't ALLOW empathy OR sympathy as a general rule but after reading up on the Webway more it also occured to me based on what @drukhariboypussy said that: they also LIVE in a pocket dimension thats the equivalent of sludge goo compared to flowing water in terms of its psychoconductivity.
Their culturally numbing of empathy has an impact, certainly, I believe but if your brain is hardwired to be hyper-sensate to the ebb and flow of the Warp and you grow up in a space where the equivalent matter TO the Warp has about 16x the viscosity then naturally your ability to USE that is strongly dulled.