It clearly doesn't. I guess we'll wait for the next RCE to learn our lesson.
> [...] vs all the bugs and issues with any code in the SSL layer.
You keep calling it SSL, that already makes me suspect that you have a few outdated preconceptions. Today you can use a formally proven TLS implementation, if you're so inclined. Formally proven APT? Will never happen.
If TLS is used, it significantly reduces the surface area exposed to anyone who can access or tamper with the traffic. None of the code that literally made an RCE possible would be accessible in the vast majority of cases.
Imagine if we would have had TLS used with APT everywhere right now, the threat would have been "if NSA MiTMs you with the certificates they can generate". Drastic difference in terms of scale, sophistication and likelyhood of it happening.
Let's compare the extremely, extremely rare edge case of this with signed packages via Debian's keyring on the local box, vs all the bugs and issues with any code in the SSL layer. And of course, that the people most able to MITM, which are often 'state actors', likely have root certs by various means regardless.
I would be astonished if for example the NSA hadn't obtained the capacity to generate certs for MITM at the drop of a hat.
And regardless, without certificate pinning, MITM is a thing with SSL anyhow. There have been quite a few sketchy SSL providers over the years, there was a deep post about how hard Mozilla works, for all their other foibles, in trying to keep bad actors out of their accepted list.
Point is, SSL isn't actually that secure, has its own layers of bugs and issues, not enough people certificate pin, and so on.