If you cured 100% of all cancer it would only reduce US deaths by 20%. Clearly we should conclude that cancer isn't a problem and isn't worth curing, and also that heart disease and unintentional injuries and so on are also not problems and also not worth trying to fix.
GP didn't say it's not a problem and not worth fixing. They're claiming this is not a good fix.
They invented a dumb fix and complained that it wasn't good. Or, since we're being artistic in this thread: pulled a straw man out of their ass and complained that it smelled foul.
I did the same with cancer/mortality to demonstrate the same trick in a setting where its flaws were more obvious. It's true that I said the quiet part out loud in a way that the post I was mocking did not, but the quiet part is especially important to debunk so I make no apology for doing so.