This is a subject I've done a significant turn-around on in the past couple years after seeing how fascism took hold in the past, and doing a fairly deep dive on the differences in policies between the 'bad and less bad' parties, and the practical outcomes of those policies in people's lives and ability to organize.
Like you, I was completely disillusioned with the system, and thought of voting in said system to be a pointless exercise. However, sometimes it can make drastic differences that can impact millions of people's lives to various degrees. To be clear, I'm not advocating for putting extreme amounts of effort into campaigning, but the critical votes (For the US, the Local State Midterms and Presidential Elections) are absolutely worth putting a vote in. If your country's votes are not completely rigged such as it is in Russia, then I would advocate participating in the vote.
So why do I think that now?
First, let's address the idea of Trump and Biden being one and the same:
While I would never defend Biden to the point of saying he's a 'good' man (he's still a neoliberal at heart, and as you say, he supports genocide), he is allowing some positive things to pass that would not happen under a Trump presidency, and some of those things can be fairly significant.
Trade Unions are having a resurgence, mostly due to the fact that Biden isn't actively trying to hinder their existence compared to previous presidents (Ronald Reagan decimated them, for example).
The Inflation Reduction Act is actually a big a deal, and is something that Trump would not have passed. It's definitely not perfect, but it will give the renewable energy sector a pretty massive boost, which is desperately needed to get the ball rolling toward helping reduce climate change. It also will subsidize our transition to heatpumps and better insulated homes, to reduce energy consumption overall. Considering how little time we have left to make meaningful change in regard to climate, this is a massive win considering how captured the government is by Fossil Fuel lobbyists.
The Infrastructure Investment and Jobs Act is another genuinely good bill that will help with climate change by putting $110 billion towards making the electrical grid ready for a transition to solar/wind energy.
Lastly, for all of Joe Biden's many, many faults, he is not a full on fascist dictator. And now comes my biggest reason for voting (not just in the US, but everywhere).
Fascist's rely on passivity to gain power.
I made a larger post about this topic here, but the short version is: When someone trying to get into office is openly fascistic, history has shown that they will do what they say when they get into power, and they will do everything possible to secure that power permanently, and expand it.
Trump is the first openly 'strongman' style fascist that has a very high chance of getting into office. He wasn't quite this fascistic in his first term, but now, especially after January 6th, there is a very real possibility of the US descending into a genuine jackboot dictatorship. And traditionally, fascist regimes help other fascist regimes around the world (And Trump has a hard-on for Putin, so Ukraine would be fucked if he wins).
Yes, Biden is committing genocide, the US is still is an imperialistic government, the prisons are still full of slaves, and he is ultimately a neoliberal that will not enact truly meaningful change on a wide scale. But even with how bad things are, they could absolutely get, way, WAY worse. We've already seen some pretty massive regressions in rights due to republicans, as other comments have mentioned.
I do understand your frustration though, especially as you're living in a country that is fucked over either way by US politics.