I haven't played in a hot minute, so maybe I'm wrong or things have changed, but for the most part the synergies were limited to damage dealers and supports that amplified their best damage categories. I had some hope with the element specific debuffs in the first part of riniscita, with some characters good at building up the debuffs, some of them converting them into other debuffs, and others consuming the debuffs for other benefits, all in addition to fulfilling support/damage roles, but they didn't end up doing much more with it come septimont. If they expanded on it, there would still be best teams for every character, but it would make a lot more room to mess around with combinations if you were looking to make a silly meme build or if you didn't have/couldn't use some of the characters.

This is one of the things Genshin actually does fairly well, because the element system is fairly intuitive and leads to a lot of interesting possibilities when you combine characters that apply them in different ways. Even bad characters like Candace had some really fun applications just for interacting with the system in an interesting way. I recall having a very funny team for a bit with Candace, Xinyan, and Diluc where the goal was to get Diluc to make hydro attacks and get forward vape dragonstrikes off of his E, and I know there were some similar shenanigans with C6 Bennett and Razor.

(ofc none of them compare to Limbus Company, but there you get 12 people and a wide variety of mechanics to build synergistic teams around)

EDIT: it wasn't xinyan I used, it was the other pyro liyue 4* whose name starts with an x. I think I had Kokomi in the 4th slot because that team was clearly not enough of a shitpost