“Be curious about what you’re writing about” is not stock Common Writing Advice but it really, really should be. There are a lot of written works that fail due to the authors just being obviously incurious about what they are writing about.
If you want to write a non-capitalist society, you should be curious: how have people tried to do so in the past, and what pitfalls did they run into? If you want to write someone fishing for subsistence, you should be curious: what do people who fish actually do? If you want to write a character who embodies all the opposite traits of your protag for the sake of being a narrative foil, you should be curious: why are they like that, and what impact does that have on their life? If you want to write a story set in a place you’ve visited once for a week or only seen on tv, you should be curious: what is it like to live there? If you want to write a scene where one character explains asexuality to another character, you should be curious: how would this individual approach this conversation, and why are they doing it now, and is this in keeping with how they’ve acted and spoken before, and would the other one listen to them? (If this is a fantasy or sci-fi or historical setting, do they have the same concept of identity and attraction as you do? How would they conceptualize and express it?) If you want to write a character of a different race, religion, nationality, etc. from you, you should be curious: what is life like for people of that experience? How do they experience the world?
When the author has not actually asked themself these questions, either because they think they already know or can already deduce everything there is to know about it or it didn’t occur to them that this was something worth being curious about at all… you can very, very often tell.
