>The final years of the Republic were characterized by fights over citizenship for the Italians, consolidation of land in the hands of a small number of slave-owning oligarchs, meaning that more and more people were unemployed and ineligible for political advancement, and politicians breaking the political rules to push their agenda (kick out the guy vetoing my popular bill) or halt someone else's (kill the guy who passed that popular bill).
The more you look the more parallels you see. Unpopular military quagmires in far-off places for no purpose but the enrichment of the leaders, dislocation of traditional ways of life, increasing political polarization, the privatization of the military, rampant corruption, endemic racism and xenophobia, battles over access to citizenship and voting rights, and a set of elites so obsessed with their own privileges that they refused to reform the system in time to save it. All taking place a few decades after a decisive victory in a long cold war, leaving Rome hegemon of the world.
I recommend checking out The Storm Before The Storm: The Beginning of the End of the Roman Republic by Mike Duncan. It illustrates the process from "hey, the rules don't technically say bills have to start in the upper house..." to all-out civil war, step by step.
well, that sounds very much like today!