Everyone makes mistakes, but not if the tools they use don't allow them to make them. Yes, if everyone working on it was perfect then you would be correct. Thankfully this is not a requirement for any profession.
In "From the Earth to the Moon" [1], someone explains that the main problem of the Apollo 1 fire was that nobody thought to label that test "hazardous". Sitting on the ground was supposed to be safe.
We should expect perfection when writing C code, but we should also be clear that writing C is a hazardous activity, and not to be taken lightly. My surgeon is a human being, so I don't expect him to never make a mistake, but he's also a skilled and careful professional, and I do expect him to never make a 101-level mistake while holding a scalpel.
If you know your tools there is less risk that you produce security bugs. You know the sideeffects of all the commands and functions. If you use a black box and trust it fully, you will (unknowingly) find ways to make new security holes noone ever thought of before.
I'm not saying that we should not innovate, just that we should not rush head first into the blue sky thinking everything is fine just because we use the new shiny thing where we can't make bugs ever.
And there are those working on mitigating some of the worst issues with those languages, maybe someday they will bear practical fruit as well.