I'm unsure of what would need to be "fixed," as my biggest criticisms of the setting's generic nature is tied to the presentation of Solasta itself. As a video game using the 5e rules, that's actually its strength, as it gives a clear baseline for which the majority of gamers will be familiar. In that case, "fixing" the Solasta sourcebook by adding more unique elements risks taking away from this core concept. Waiting until Solasta 2 comes out and seeing what it contains may be the best approach.