We do have the ability to regulate the people in power by not voting for them in the first place.

So if there are only 2 people on the ballot, and you don't want either, what are your options? If the DNC is actively working to prevent others from getting on the ballot, leaving us with only 2 bad choices, and you go along with it, you haven't actually 'regulated' anything. Dangling a false choice in front of people to create the illusion of agency is nothing new, and it's very much what US politics at the national level is.

Want to 'regulate' the ability of the US president to enable a genocide in Gaza? Too bad, because all of the candidates that the parties will let you vote for, will all enable the genocide. Believing you actually have real control over the US government is a lie you tell yourself.

use it to give power to someone who wants to do away with democracy

No one here is talking about voting for Trump, and the rhetoric of 'not voting for Biden puts Trump in office' runs directly counter to your argument that we have the ability to regulate who gets into office, because you're explicitly arguing that it's a binary choice and it's a moral imperative to put one of those people in power.

I can't both have to vote for Biden as a moral imperative to stave off the death of democracy, and also not have to vote for him, in order to regulate his ability to wield US strategic power to further a genocide. It's a false choice that's been forced by the political parties' shutting-out of other parties and candidates, but pushing a button every 4 years makes you feel like you had an impact.

any frustration with Biden... must be squared against the fact that we have to put a candidate up against Trump

Of course, which is why my real anger is directed at the DNC. They didn't learn their lesson in 2016. They put Trump in power by shoving through their preferred candidate, despite her being mind-bogglingly unpopular. Biden eked out a win in 2020 because people hated Trump enough and he was still fresh in their minds, but the reality on the ground now is that Trump has been gone for a while, and most peoples' lives have not gotten markedly better under Biden. Biden's promise that "Nothing will fundamentally change" has proven true, and I think there are too many voters who will not turn out in force to vote against Trump this election, just as they didn't in 2016. And Biden is wildly unpopular, to boot.

Just to be clear; if Biden is the candidate in the General election, I will probably vote for him(because what the hell else can I do? Any actual good candidates were bullied out of running). But at this point, I don't think he's going to win. I think the apathy towards his insubstantive actions, combined with the very valid and justified anger over his aid in the genocide in Gaza, is going to lose him the election. It doesn't matter what politically-engaged people like you and I think, if the average person isn't on board with him, and they're not.