New study finds vast majority of diseases have only a very small genetic contribution of 5% to 10% at most (so much for 23andme testing)

[Wishful]

Many genetic mutations seem to normally be there for a reason.

I think that depends on how old they are. If a variant has been around for thousands of generations, it's doing something useful, or at least no harm. If it's only a few generations old, its value is unproven. Some genes might cause more problems than benefits, but there's no easy way for mutation to remove or replace them, so we're stuck with them.