The problem with Quantum Immortality is that it is a pretty horrible scenario. That's not an argument against it being true of course, but it's an argument for hoping it's not true.

Let's assume QI is true. If I walk under a bus tomorrow, I won't experience universes where I die, so I'll only experience miraculously surviving the accident. That sounds good.

But here's where the nightmare starts. Dying is not a binary process. There'll be many more universes where I survive with serious injuries then universes where I survive without injury. Eventually I'll grow old. There'll be some universes where by random quantum fluctuations that miraculously never happens, but in the overwhelming majority of them I'll grow old and weak. And then I won't die. In fact I wouldn't even be able to die if I wanted to. I could decide to commit suicide, but I'll only ever experience those universes where for some reason I chose not to go through with it (or something prevented me from going through with it).

It's the ultimate horror scenario. Forced immortality, but without youth or health.

If QI is true having kids would be the ultimate crime. If QI is true the only ethical course of action would be to pour all humanity's resources into developing an ASI and program it to sterilize the universe. That won't end the nightmare, there'll always be universes where we fail to build such an ASI, but at least it will reduce the measure of suffering.