> Further, given an illness that kills with lets say 50%, and that is influenced also by genetics: If we can now cure that, so make more people survive and reproduce with this, while factors and genetics stay: isn't it expected we may see this illness raise in the population?

Illness that doesn't kill before reproduction is irrelevant. Evolution is about spamming copies of yourself more than other strains of organism, and getting cancer at 45-55 is moot if you have 3 kids and a retirement plan mostly completed before then.

plus genetically we're still basically cavemen, even if you can find pressures for things like dairy or alcohol tolerance in certain populations.