Your scenario would save lives, but we have no way of knowing if we are in that scenario.
If you know that after ten thousand deaths, the technology will be good enough to start saving more lives every year, then your utilitarian argument works. The problem is that you can't possibly ever know that in advance. It's equally plausible that the last 0.001% will take decades to solve, or even remain out of reach indefinitely. Then you just threw away ten thousand lives for nothing.
This is why the burden of proof needs to be on the new system, and why the precautionary principle applies.
If you know that after ten thousand deaths, the technology will be good enough to start saving more lives every year, then your utilitarian argument works. The problem is that you can't possibly ever know that in advance. It's equally plausible that the last 0.001% will take decades to solve, or even remain out of reach indefinitely. Then you just threw away ten thousand lives for nothing.
This is why the burden of proof needs to be on the new system, and why the precautionary principle applies.