How realistic is Rome: Total War?

I’ve started playing the game recently, and I’ve been having a lot of fun with it.

I value realism in war gaming very much, and while I’m very knowledgable about modern war, technology, tactics, and weaponry, I know very little of the Roman era.

So I’m curious - is this game considered generally realistic, a real reflection of what Roman era battles could be like?

It strikes me that the pace of battles is very fast, much faster than I’d expect is realistic. But to some extent, that may be a result of where I’m at in the game - I’m fighting against Gallic light infantry, which I gather is more like a group of warlords gathering their men together than a trained, disciplined army. And in that context, it might be realistic that I can break them easily and inflict pretty ridiculous casualty ratios. Rome did have a lot of military success, after all - especially early on. Perhaps the flow of the game will change as I get further in the campaign.