We can arrive at “good” behaviour by intellect or emotion, that we can reason our way there or by compassionate senses be compelled to it, but politics removes both sensibilities from the equation.
If you are a powerful leader and you want to do the right thing by people then you will have to convince people who can move society to move it. Preferably you would like them to move society in the direction you have calculated as the best direction but usually the cost of getting those who can move society to move it is that they see a return for their contribution. So this results in tweaking the direction we move to make it worth their while, that it is better to move in general than to not move at all, even if it is not the desired direction.
Politics is the act of balancing appeasements, negotiating compromise between the best interests of the people and the selfish interests of the powerful (often there is a third consideration being popularism; the people know what they want but they do not necessarily know their own best interests).
So the system is very much designed to deliberately fail.
So given this information we can go back and see why Plato was against the Democratic empowerment (election) of Senators; that if their job depends on appeasing popularism then society will move in a direction that is for majority preference but against majority best interests, as Mum would have us eat our veggies before allowing dessert so to speak.
But Plato also highlighted how wealth is a great driving force but a terrible decider of where to drive towards, notably “Wealth is great as wind in the sails but should not be navigator of the ship” pointing out the conflict of interests that come with Aristocracy, Oligarchy, Plutocracy, Corporatocracy, whateverocracy, etc.
Plato distinguished that the duty of the Senate was to do what is in the best interests of society/humanity regardless of politics; the last place politics should be is in government, that all leaders have a responsibility, leadership is not an opportunity but a profound privilege. The right to lead should entirely depend on not being corrupt, not on the employment of corruption to empower the right to lead; ergo “Power corrupts, absolute power corrupts absolutely” if you cannot lead without corruption then you shouldn’t lead, if that is the Senate, Military or even economic leadership positions, in fact any leadership role of note.
Democracy is not what we have made it, in essence Democracy is not popularism or majority rule, it is the opposite of this, that every citizen is individualised as a political unit, we have come to use it as equality of the power of a vote, but it is really about the right for each citizen to contribute to the development of valid solutions in the direction of society.
Democracy works best confined to the Social Arena, just as Capitalism works best when confined to the Economic Arena, but we have allowed both Democracy and Capitalism to spill over into the Government Arena, ultimately resulting in the politicisation of the Republic (or modern stylised versions of it).
We could use Democracy to empower anti-corruption watchdog authorities over the Republic government process, but not to fill the government. However if watchdogs are elected and re-elected by their actions then people will be more inclined to elect watchdogs that enforce popularism, so there would have to be genuine measures in place to ensure this does not occur, that is the catch 22 of watching the watchers. But then the more “Watchers” there are the less chance of corruption, you just need one honest watcher.
The ideal system would not have Senators perse, but appoint leading academics to a temporary Senatorial role per issue in order to build a valid direction with other leaders of fields that hold a stake in the outcome of that particular issue. The ideal would also include the general population having access to the discourse and the ability to contribute to it as per the Social expression of Democracy, but of course the formulation of options would have to stand up to peer reviewable scrutiny in order to eliminate the popularist and economic biases that will invariably arise.