During the republic, the romans did not waste a second on defense. They simply put almost all of their offensive capacity into one province / front, e.g Hispania in the 1st century BC. Well, I am overexagerating a bit. But these republican romans were that thoughtless. And surprisingly it worked more than often. A lot of luck involved.
During the principate, the romans had a princeps, who had the responsibility to secure ALL the empires borders reliably. Something no roman proconsul of the republic ever had to do or was even willing to take into consideration!
As a result of this increased reponsibilty of the emperors, they had much less units rest for offensive campaigns. Every roman emperor knew, that he can't do a multi-front war. That is why Augustus cut a deal (peace) with the parthians.
The republican commanders just 100 years ago or less knew the same facts. They simply did not care! Because they acted recklessly and only focussed on increasing their own and their families honor. Regardless, if this was beneficial for the republic or not (e.g. Caesar, Pompeius, Crassus, ... and almost all others). This detriemental and subversive nonsense ended with Augustus!
So no! Looking to the big picture most republican commanders were just a piece of selfish shit.
PS: Even if Hollywood and HBO prefers republican commanders over imperial commanders