While I have a deep interest in the US and I think a better than average grasp of its political history, I'm really not equipped to talk about most of it on the level this sub expects.

I do know something about Rome.

The, well, let's call it "traditional" position is that Rome was in most ways an oligarchic state, governed by family connections and ties of patronage. That position is perhaps best articulated in the anglophone world by Ronald Syme, who said something like any system of government, whether its name is monarchy, republic, or democracy, once you get behind the facade is in fact an oligarchy.

Syme said that in 1939, after doing a prosopographical study (a study of known individuals, charting their careers and connections) of the end of the Republic leading into the monarchy Augustus established. His contention was that Augustus came to power by enabling one set of aristocrats to supplant an older one. A man appeared great because an interested body of relatively disempowered men found someone that could express their political ambitions against another closed and entrenched body of men. The line he used there was something like the outsiders chose an equality of slavery instead of an unequal freedom.

You might be able to imagine what was going on in 1939 that might make Syme start to think that way, but that's another issue.

So you're not wrong to start with the idea of Rome being a strong aristocracy. Likewise, the loss of what you call the "middle class" - a problem the Gracchi noticed and tried to redress - is also part of the traditional narrative - indeed, a much older narrative than Syme. "Middle class" is of course entirely anachronistic. What Ti. and C. Gracchus were bothered about in the mid 2nd century BCE was a perceived dearth of men with sufficient wealth to serve in Rome's armies. Until Marius a generation later, soldiers were generally (but not always, Scipio Aemilianus' army in Spain was one such exception) expected to fund themselves, and their capacity to do so was judged on their possession of land. A man with such-and-such land could be expected to supply so-and-so for the campaign. By the mid 2nd century BCE these men were becoming difficult to find. The Gracchi figured this was because of the introduction of industrial farming powered by slave labor to Italy, driving the "middle class" off their property (since they couldn't compete on industrial scales), and hence reducing the number of men qualified to serve in the army. That's the problem the Gracchi set out to fix.

EVERY ANCIENT SOURCE THAT COMMENTS ON THIS MATTER AGREES ON THIS NARRATIVE. That's all in caps because of what I'm going to say a little bit later.

Where you do make an outright mistake is your characterization that being Patrician had something to do with being a senator. In Roman mythical history, Patricians were people descended from Romulus' 100 besties, and Patricians early on (again in the mythical history) were the ones with access to political and religious offices. Whether THAT narrative is true or not, by the time of the Gracchi the Patrician lock on public life had long been broken, and indeed the Gracchi could not have done what they did if the Patricians still had such a lock, since they were Plebeians, not Patricians.

Now, that first narrative, the one about Rome being an oligarchy? That's being revised. Starting with Brunt, proceeding through Lintott and especially Yakobson, more and more we are starting to appreciate the weaknesses in the oligarchic cabal. Clientele looks weaker than it used to. Elections seem to have been honestly contested, which implied the vote is really up for grabs and politicians wouldn't just assume their buddies would vote for them. Cicero's brother Quintus wrote a pamphlet about winning elections that makes it pretty clear a politician needed to be hassling even the people he thought would be solid to get their votes. Families aren't really tight political units as we used to think. Cicero hated the introduction of the secret ballot, which implies he knew people were voting in ways they wouldn't admit to if challenged by someone like Cicero. Bribery, by all appearances, was effective, which means money was a way of breaking whatever lock the oligarchy had on the elections.

I don't want to say Rome was "democratic" by modern standards by any measure, but it wasn't the kind of ossified oligarchy you're alluding to.

Now, that bit that got me so bothered earlier, that bit about the Gracchi....

Well, Rosenstein thinks it didn't happen.

He doesn't think the Gracchi weren't trying to solve a perceived problem - a problem ALL THE SOURCES REPORT - the dearth of men qualified to serve in the army; he thinks they WERE trying to solve a problem, but their problem didn't actually exist.

Seems there isn't archaeological evidence of that industrial farming in Italy to which the Gracchi attributed the dearth of the "middle class" soldier. Small farms seem to have trucked along just fine. That's not to say there wasn't a dearth of soldiers; there was. Rosenstein proposes that instead of a dearth being due to the lack of men with sufficient property qualifications, the dearth was due to unpopular wars being fought a long way from Rome for very little gain among the rank-and-file. Land distribution was preferable to military service as a means of improving one's lot in life. Rosenstein published in 2004, and you can imagine what might be going on in his contemporary politics that might make him think of unpopular wars, but that's another subject.

If Rosenstein's right, every ancient source that talks about this is wrong, and that's deeply unsettling, but as far as I can tell no one's found anything more than a general icky feeling to present against Rosenstein's argument.

So, I would amend your view of Rome. The oligarchy we don't think is as tough as we used to think it was, and there's a pretty good argument that the land crisis didn't happen, at least not in the way the sources describe it.

What that has to do with the US and particularly Bernie Sanders, I don't have a bloody clue.