I think the main point is that a good alternative C doesn't compete directly with C's strongest points.
Here, you can of course make a more safe language without runtime penalty just by supporting richer build-time/static checks, but the modest and meaningful gains you make within that constraint will never be enough to displace C.
You need to be providing something meaningfully more in areas where C hasn't already squeezed out most gains. The OP tastefully avoided making this article directly about C3, but if you go and look at the summary of features, you can see how this philosophy connects with what they're working to build.
Here, you can of course make a more safe language without runtime penalty just by supporting richer build-time/static checks, but the modest and meaningful gains you make within that constraint will never be enough to displace C.
You need to be providing something meaningfully more in areas where C hasn't already squeezed out most gains. The OP tastefully avoided making this article directly about C3, but if you go and look at the summary of features, you can see how this philosophy connects with what they're working to build.