Anne, I agree that not every story is epic. My novel Firedancer started as a stand-alone and went into the drawer for 10 years before a publisher approached me wanting to see my long fiction (she'd only seen my short stories and was impressed). She only buys series but she wanted Firedancer, a lot. Ergo, now it's a series, but I admit it's been hard to wrap my head around extending the plot of a book written and stuck in the drawer in 1999. It's all good, as there was sufficient story there, but what's wrong with stand-alones?
I think there is serious peril for a writer of series to get pigeonholed by fans into expecting them to write the same thing forever (JK Rowling, Jim Butcher). My stuff is all over the map, from alternate history to dark fantasy to soft SF to epic fantasy. I have had the freedom to write what I want because for a long time I wasn't serious about publishing it. (Now I am, because having freed myself from a day job, I don't ever want to go back!) Be that as it may, people reading my stuff never know what they're about to pick up, but my first readers are always eager to see it. Is variety in your writing bad? I don't think the writer should have to stick to one trope just because people expect more of the same.
I like continuing series as much as the next person, and heaven knows, I can't seem to write short novels, as my mind continually spins out epic yarns. However, if I like an author, I am willing to try anything they write, and even stick with them if one book disappoints. Nobody hits home runs every time.