Fate/Grand Order V - Salty Theoretical Phenomenon

[Resileaf]

Again, as others have said. The writers have actually acknowledged that this was a mistake - Romulus, being both a demigod and a founder of one of the Foundations of Humanity, really should have been a lot more powerful. As the character points out, he is conceptually Rome. And since so much of modern civilization is built on Rome, then conceptually, he is one of the foundational elements of modern civilization. He should, in theory, basically be a god of the modern world.

I'm well aware, I brought that up later in the thread. :P

In-lore, Rome's founding is one of the most important thing that's happened, as one of the most influential civilization of history.
I'd say more, but that's spoilers for future Lostbelts.