@AaronArx You have to register the game in order to see those forum sections
Anyway, I'll go ahead and post the suggestions I made:
So apparently materialists/fanatic materialists require either the RNG (Random Number Gods) to bestow the trait or trigger a rare anomaly (which is even harder to get since the AI players gobble up the anomalies

). i checked and while the wiki says this: "Materialists are also unable to access psionics research by default, while Spiritualists have the same issue with robotics (though both can still obtain them as research alternatives by employing a scientist with the proper expertise)." spiritualists have NOWHERE NEAR the same amount of difficulty that materialists get, all spiritualists get is a small malus which is easily overcome with a scientist of the needed expertise.
So, my suggestion is to balance things out by either making it that much harder for spiritualists to get droids, or maybe synths, or adding other methods of getting the PSI tech or the trait.
Here are some deas for making it easier to get the trait and/or the tech, the easiest way would be through some kind of event:
1. Give the currently existing event a higher weight/chance to be found.
2. More events in general that can give the trait. I saw a psionic horses thing in the events text, never ran into it myself though, and one of the creatures in the specimen collection mission is weakly psionic, so, maybe some stuff about psionic creatures or something. Basically, the more events that give the trait, the more chances it'll actually happen.
3. Since Zro, Stellaris's version of melange of Dune fame (you even have the Navigators Guild reference in there and all), is researchable, I had an idea of involving the stuff. For starters, you'll have to have the zro resource being mined, then perhaps there will be some random event or event chain with a mean time to happen that involves experiments with zro or something, don't know. Obviously you guys don't want to have too many references to substance consumption in the game, so, I'm not sure how you'd go about involving it. I'm thinking mostly of Dune here.
4. This one relies on a neghboring empire having researched the tech: Some kind of random event or perhaps an event chain that involves a renegade scientist (or one seeking asylum or something) from another empire that wants to bring the PSI tech or perhaps has the trait.
Alternatively, you could make it that much harder for spiritualists to get the robotics (or maybe just sentient AI) tech, but I have a feeling that idea wouldn't be too popular.
What I'm trying to say here is that there is a massive imbalance in the difficulty of the two ethos getting the tech that is basically on the opposite side of their ethos and one or the other needs to be changed.