Meta-plot construction tips?

I'm an RPG author (yet to be published), and I've ran into some constructive criticism that I can't figure out how to solve in a good way.

All my settings seem to have a pretty dull meta plot or meta story. They all pretty much boil down to "A great empire once ruled the entire world. It fell, and now people pretty much do whatever they want." It's useful for several settings, because it allows for me as an author to construct adventures in many different settings and environments without having to leave the comfortable bubble of the world I have created.

However, someone on another subreddit pointed out that this story has been done before, especially in fantasy, cyberpunk, and steampunk, which happen to be my favorite genres to write in. And more devastatingly to me, It's been done far better than I ever could, like in the Foundation series by Isaac Asimov.

So What are your best tips for coming up with an interesting meta story for a fictional setting?

I'm looking for you best tips, your methods, your modes of thought, strategies, cheats, tricks, schemes, conspiracies, anything I could do, here at my computer with google docs that could even slightly, potentially lead me towards inventing an original, engaging, supportive meta-plot for a fictional universe. Any fictional universe.

I'm not saying there's a formula whereas a meta-plot can be made objectively good by following any set of rules. But I'm a systematic person. I like to have a method for these kinds of things. Comes with the RPG hobby, I suppose. I posted this same question to the r/worldbuilding subreddit, but it got removed because it was too writing-oriented, and I was directed here instead.

Thanks beforehand. Happy writing.