It's a bit complicated. That survival rate primarily includes people who become severely ill and seek medical attention. Since it's the most severe cases, the case fatality rate (CFR) will appear higher.

HOWEVER, what also needs to be emphasized is that a disease with like a 10% CFR is probably a civilization (as we know it) ending disease. I believe covid 19 was between like 1-2% and we saw how it nearly broke our health care system, and that was with people more competent than RFK in charge.

If a disease emerges that spreads as easily as COVID did and with a CFR rate 3 to 4X as worse, it'd obliterate the health care system very, very quickly. Then people are going to start dying en masse from preventable diseases, like common infections, moderate injuries (e.g. broken leg) etc.

If a disease emerges that spreads as fast and far as COVID and has a 50% CFR, yeah that'd collapse most societies completely. Maybe some societies that can truly lock down and enforce social distancing, like China, could survive long enough for a vaccine or other solution to become available.