I feel your frustration, but bearing witness is not useless. It just feels so lacking because a lot more is needed. But bearing witness is really the first part of Israel's reckoning.
I've been following the conflict since I remember existing. The impunity was always a source of frustration, but it was also how most people had no clue what was happening. Talking about the conflict you'd often get well-meant replies saying "oh, that war has been going for thousands of years" and "it's a religious conflict". People had no clue about the Nabka, the settler violence or the whole way Israel was created.
The October 7th attack changed all that. While the initial reaction was of outrage against the Palestinians and solidarity towards Israel, as soon as the IDF's methods became mainstream knowledge everything changed. The public relations operation Israel had which was successful so far, completely collapsed. Now the whole world is bearing witness to what Israel is. The mask of being a beacon of democracy in the region, fighting against Islamic fundamentalists has completely fell appart. Now the whole world can finally see them for what they are and there's no going back.
Notice how only extremists and anti-islamic sentiment now defend Israel. Normal people just avoid the subject or are outright horrified. But they can't do anything? Not for now, but the isolation towards Israel is becoming a lot real. And they are getting more desperate and erratic. Eventually they'll make an error that will bite them in the ass: commit such an atrocity that even the US can't justify, attack Turkey, etc.
The real question is how the Palestinians come out of this. Because, for a while now, it's clear that Israel is doomed. They have destroyed themselves when they went full-genocide. You can't ungenocide. The label is stuck, the isolation is real and nobody, besides the US, would lift a finger to help them if they were suddenly attacked by their neighbors or Turkey. But the US is not exactly stable right now, is it? When shit hits the fan in the US, Israel is on their own and they are doomed.
So, we have to do this. Keeping talking about it. Let everyone know and don't let anyone forget. And when the IDF goes too far don't allow anyone that is defending genocide to pretend they were always on the good side. Let the genocide enablers be shamed and ostracized for being the psychopaths they are.
Bear witness. Information is everything.