(Just my opinion)

I completely agree with everything you point out. The argument I am bringing up is not about implementation, it's about "if they didn't use C, they would have less (security) problems": No.

C is the way it is towards secure coding because there are compromises to satisfy other dimensions. <Fancy new language that promises to solve all of C's problems> is either making huge sacrifices in these other dimensions or is at best an experiment.

We understand C's weak points so well (due to being widespread, battle tested, really simple, or what have you), that most of the time it's safer (read: more secure) to tread dangerous well-understood territories carefully than uncharted ones only promising to be safe.