There’s a short story by Harry Turtledove titled “The Road not Taken.”
You should read it.
Basic synopsis: The secret to faster-than-light travel is trivial. It’s incredibly easy. So easy, in fact, that most species become spacefaring pretty early in their technological development. But, for one reason or another, we just never noticed it, and never developed the technology. So where other species’ development stagnated as they put all their resources into interstellar conquest, we just… kept developing. So when aliens find us and launch their invasion, we kick the complete and total ever-loving dogshit out of them and steal their technology. Look at me. I am the captain now.
It’s relatively short, available online, and you could probably read it in 20 minutes. It’s definitely worth a read.
