You want to hear a left-leaning opinion about this in isolation from what Trump has been accused of.
Well, okay. I don't like what Biden has been accused of. Don't like it one bit. Biden was one of my least favorite Democrats running in the 2020 primaries from the get-go, and this new allegation underscores it. I don't "believe all women" myself, but I believe most women, which is what FBI statistics suggest we should do.
Unfortunately, politics now presents us with two choices. Barring unforeseen circumstances (or perhaps not so unforeseeable: like a death from Covid), either Biden or Trump is going to win the 2020 election and be President next year.
So, in order to objectively assess one's vote on this issue, one must consider all the publicly-available information regarding both of them. And on the issue of sexual assault, taking all the allegations against both candidates into account, it's not even close. I will spare you a link this time, because I know you're smart, and all the stuff on Trump is readily findable using a quick Google search.
I have voted third-party in the past (like in '16, when I didn't like either HRC or Trump), but Trump's atrocious conduct over the past 3+ years makes me less inclined to do that this time. I still plan to vote Biden in November, despite my reservations.