We all know the saying "Rome wasn't built in a day." Worlds in novels, especially fantasy ones, are the same!
(Yes, world-building also applies to the "real world." Even if your story takes place in our world, you'll need to establish a time and place, along with all the details that fall in those.)
Writers tend NOT to spend enough time world-building. Worlds never exist to serve one character; don't write them that way.
Also, even fictional worlds have some structure to them, so elements shouldn't pop up only when the character needs them.
Example: a character needs a wand; suddenly the previously tree-less location now has a bunch of them, AND everything that needs to fall into place conveniently appears.
Or, in a world with magic, people's powers are only mentioned when the main character needs them.
Many authors don't want to spend time on this, but cutting corners becomes obvious down the line.
You don't need to (and shouldn't!) dump every detail into your MS, but the more you weave in, the more immersed your readers will be and the more context you give your characters.
On that note, remember that all worlds have some structure AND some chaos. Not everything makes logical sense, but most things fit together.
Be careful with parallels, especially in regard to ethnicities and identities. Always write with sensitivity, respect, and care. I can't count how many authors have lost their readers (and written books that didn't serve their audience OR their stories well) because they didn't do this. Sensitivity readers are a great idea, especially before you reach out for editing.
YOU ARE READING
From an Editor: Common Writing MistakesNon-Fiction
As a content and copy editor, I see mistakes that many writers make. I've compiled these into some quick tips and examples for anyone who may find this helpful. (Adapted from a Twitter thread I wrote.)