I came here with the exact same complaint, and lo and behold, it is unsurprisingly not only already made, but also disappointingly left to rot like it is everywhere else.
Is there a way to block those placeholders? When I block something, I want it to completely cease to exist on my end. None of these placeholders constantly reminding you that the blocked thing is still making useless noise right beside you, and there's no way to make it stop; in fact the system itself will make useless noise on its behalf.