You are making your own criteria to validate your argument!
Yes, a republic is rule by representatives (just as Rome was), but there is no element in the definition of republic or even representative governance that specifies whether it be proportional or not. So there is NO REASON our representation cannot BE prortional.
Advancing the argument that is SHOULD be proportional is NOT arguing for direct democracy.
The senate is NOT, contrary to your assertion, an argument for or against proportional representation. The senate wasn't created with citizens in mind at all. The constitution was written when the mindset of Americans was not that they were Americans first, but rather, they were citizens of their respective states. So the senate was there to represent the each state as a whole, and use it to offset the power of larger populous states in the federal govt.
These issues were all comromises well documented and in no deliberate manner were they considered to be holy writ handed down.
You are really mixing and mis-labeling things to make your propaganda work.
Enabling more people to vote is NOT advancing direct democracy. Giving the vote to women and to blacks was NOT advancing direct democracy, it was merely giving more citizens a say in who our representatives were.
Ineligible and non citizens are not VOTING-and if that has happened on occasion is certainly NOT at a level to alter the outcome of an election. Those "control' features are merely dog whistles and cover for voter suppression especially of cities and minorities.
The ballot harvesting you cite? Republicans are doing that in California, NOT Democrats.[1] California law allows for third party ballot return, but it is REPUBLICANS putting out unofficial ballot boxes. This issue is being addressed in the courts, I believe.
Regarding your assertion of the We the People act [2] you present misleading information. What is the problem with getting people who are "otherwise not interested in voting" to actually vote? It's called advocacy and we try to do that now with direct mailings, knocking on doors and phone calls. It is your assumption that people who submit ballots had no interest in voting. I would say that they DID get interested hence them turning in a ballot. IF they were not really interested they still would not vote.
And yes the present debate DOES indeed infringe on people's rights and abilities to vote as various states pass voting suppression and inhibition type laws. Idiocy such as limiting all counties in a state to one or two ballot drop boxes when some counties have thousands more people than others?
I am opposed to gerrymandering and here in Michigan voters replaced the legislature's power to do this and installed a bi/non-partisan commission to draw maps. But in states where this hasn't happened, I am all for Dems to do so because we know Republicans will. I oppose unilateral disarmament.
[1] https://www.abc10.com/article/news/politics/elections/yes-ballot-harvesting-is-legal-in-california/103-067a65c5-9bde-4ff4-a815-97dee5597597
[2] https://www.politifact.com/article/2021/feb/03/fact-checking-misleading-attacks-hr-1-democrats-vo/