You can have setting notes about cultures while both keeping things useful and relevant and not ramming a 200-page tome down the players' throats.I feel a lot of world builders fall into the trap of making too much mid-level canon, for example, detailed histories or setting notes about cultures. It might feel like fleshing out a world but in practice a lot of that sort of work never really informs actual play, sitting a couple of degrees more abstract than things the players will actually interact with. Often it feels quite sterile to read as well. While it is necessary to have some sort of big picture in mind to hang things off, this gets into diminishing returns pretty quickly, and can even be counterproductive to go down too far.
I think a better approach is to have some sort of big picture to hang the bits together, but then to largely focus on detail that directly affects the adventures - drive the canon off what you need for the adventures. This keeps it (a) useful and likely to be relevant and (b) more likely to feel 'lived in' rather than static and sterile, as it is designed to be used in an adventure. It also lends itself to a show-don't-tell approach to exposition.
Plus, if you drip-feed your setting canon rather than ramming a 200-page tome down players' throats it's more likely to keep them interested and wanting to see more.