Technology has never been static. Progress has been slow, but it has always been there.
That's the point, if it's sufficiently slow as compared to the length of the wars, then innovation/progress is not a deciding factor in wars. What counts is what you can mobilize (or have at the start) of a war.
Imagine a European-style army from 1900AD army fighting an army from 1950AD. The 1950 army wins, even if it's outnumbered. Innovation in weapons and tactics counts massively.
Imagine a Roman-style army from 100AD fighting an army from 150AD -- innovation in weapons technology or tactics is unlikely to be the deciding factor. It's who has got the more troops who wins.