I mean it didn't conquer too much to make an impact on the world, yah it had great engineering feats but so did the Chinese, the Arabs, the Indians etc. Yah it conquered alot but the Islamic Caliphates conquered more, ALOT more that had a greater impact on world history and scientific development, and yet in history classes they're just skimmed over while the Roman Empire is raved about alot. Moving on the Mongol Empire conquered MUCH more and had an even greater impact then the Roman empire, all the way from Korea to The Ukraine to Egypt, a testament to this is that Baghdad before the Mongol invasion was one of the most prosperous cities in the world, after the Mongol invasion however it never got to the richness and prosperity it once had. And yet again they're not as talked about in detail as say Greece or the Roman Empire.
I might even move onto say Caesar is even MORE overrated, he just conquered a big country of barbarians by laying seige to its capital, not a huge strategic masterpiece at all considering he did it by walling it in, he tried to conquer Britain, but failed. He changed the Republic to an Empire, but I can't think anything else he did or anything to make him the iconic leader of Rome. Later leaders would conquer much more then he did and again, I don't recall any of them making a difference in world history beyond Europe.
It could be arguable that the Roman Empire inspired the European ones, Russia more then any other, so in that sense its important as these empires would basically conquer most of the world and bring into submission the rest barring a few exceptions.