Once you learn how to understand and apply historical materialism and break out of capitalist canards like the myth of barter, it becomes much easier to come up with the things that make societies feel evolving, nuanced, and alive: internal struggles, subcultures and countercultures, political movements, economic bases, social mores and customs. That, plus having a variety of real-world examples to draw from to avoid falling into the trap of capitalist realism.
Samesies. I'm not so great on reading the big books of theory but I've passively absorbed and put together enough bits of theory that the world just makes sense to me in a way it didn't before, and I'm thinking about the sources of conflict and factions that might arise from them. Eastern jungle continent being soft-colonized by the recovering war-ravaged west? Northern settled lizardfolk kingdoms are all too glad to let the western corporations and privateers slaughter the southern nomadic tribes clearing land for rapid cash-crop farming with time acceleration. They get to expand and secure more territory and make more money selling spices and their superior alchemical compounds to the traders who enjoy the protection of the Peacekeepers (probably need to change that name) who patrol the edges of the protectorate against piracy but simply don't have the resources to go out protecting those poor tribals against the outlaws who leave the protectorate against the rules of the charter! Also yes they're stocking up on alchemical weapons that technically do not violate the ban on non-lightning weapons since they're not elvencraft in origin, and choking gas is just too damn useful of a tool to leave by the wayside. There was a riot in that dwarven factory town last week, nipped that shit in the bud. There's no nobles anymore, no need for revolutions. Also have you tried this coffee stuff? Or chocolate? Don't know why the tribals are just sitting on that shit and spend all day hunting. Don't they know they could make tons of money fast-farming it themselves? Their fault for dying tbh
Yeah, this is what I'm talking about. These are all the ingredients for a story that's better than 99% of the fantasy drivel that manages to get published.
I've got an idea kicking around in my head for a take on sirens: their don't lure sailors to their doom with their song, they just have really nice singing voices. But their villages tend to be built in shallows in the way of shipping lanes used by trade companies, and gosh, wouldn't it be convenient if we had a reasonable-sounding justification to clear them out?