One interesting question always to ask is what happens they your characters die, or when an important object is destroyed.
This CAN change everything, The best example of this is Ned Stark, his dying made everything much more interesting then if he had lived. Never forget that a book can be sad, or depressing and still be good. It can not be boring and be good.
I am not saying you should kill characters just as a cheap way to make your book interesting. However it often will not occur to you because you have so much invested in them. You should think about how you characters would/should die, even just as an exercise.
For example, Spock in Wrath of Khan dies in a way only he would. It made the movie much better then if they had found some easy way out, it gave the movie a weight that it would otherwise not have had.
One, often subtle, distinction you need to make when your making cultures is the difference between cultural norms and limits.
A norm could be something like “Women should become mothers and stay at home.” But there could (and would) be exceptions, even if they were rare. If you made it clear that ALL women were wives and mothers I would assume that I was missing something. Also noteworthy is that with norms you might have no enforcement of this other then social pressure, mostly likely from the group itself.
A limit could be “Women ARE wives and mothers.” This would mean that there are no exceptions allowed. This would also mean that you would need something external to enforce it. There will always be outliers who want to swim upstream, even if they only want to do so to prove they could.
The thing about world building is that you CAN do it for years, and never finish. After all if you wanted to write a backstory of a world with the same level of detail that we have for the Earth how long would it take?
I can’t say how others do it but I tend to do my worldbuilding in stages. When I was starting to write my first book I wrote enough about the major powers, and enough of the overall timeline to have a basic idea about what was going on. I needed to know what kinds of tech they would have and stuff like that.
As I finished the first draft I realized I needed more so I gave it another pass and added many more details.
Around the fifth draft I did one more last long pass, I went into detail about all the major political factions within each power, enough that I could write stories set anywhere I wanted.
I did this in stages partly because I did not know what I needed until I got there. It was also helpful because worldbuilding is some of the most brain taxing work you will do, doing it all at once can be hard to impossible.
If you are from the west a great many things will be normal are VERY abnormal historically. I am not saying you should just assume they change back, but don’t assume things that started changing fifty years ago, and are changing today will freeze as they are now.
For example, for most of human history, people were adults when they could do the work of an adult, for a woman this was somewhere between puberty and 16 or so. For a man, this was when he was big enough to farm/hunt. Adolescence did not exist as a concept.
If I was forty and got engaged to someone who was sixteen I would be, to say the least, looked down on today. No one would have cared a few hundred years ago.
I don’t think I need to say how much EVERYTHING surrounding sex has changed in the last century, there were times and places when women would not let themselves be seen when pregnant (not even in church).
Various societies have changed how they used makeup, from only tacky women using it, to men, to everyone.