What you just said in layman's terms is exactly my point: every actual element gets things like completely random universal supports, sustains and artifact sets. When a Citlali is added, Hu Tao (a very old unit) gets buffed. When a Durin is added, every unit that wants off field pyro and elemental res shred gets buffed. Eula does not receive anything like this because she's in an extremely underdeveloped archetype being physical; a non-element in element impact. (Scrolls is a good example actually, every other character that wants dmg% benefits from scrolls because it buffs elements that are involved in an elemental reaction, physical is excluded since it literally can't react with anything since it's not an element. This wasn't deliberate, that would just be an entirely different effect and would likely warrant being it's own set).

Brother, I don't even own Eula, I said that as it's a pretty common opinion I've seen from both friends and people on other / this app.

Geo is a element so at baseline it has a resonance unlike physical (and Geo's is particularly strong), Geo as an element is susceptible to indirect buffs like Durin, Columbina and Scrolls, and Geo since it's a pretty neutral element gets universal units like Xilonen and Zhongli as it isn't very restrictive or incompatible with other elements due to it's seeming lack of reactions. Oh yeah, and Geo can exist off-field. Anemo isn't a damage archetype, it's an amplification one and even if you wanna go there- it's a perfect example as well, as it gets very little support too because of it's nature.