You do realise that the main source of dangerous vulnerability is low level infrastructure that do not come from these package managers ? The purity and capabilities sadly solve nothing when the source of the problem is the fact that NTP, OpenSSL, OpenSSH, the BGP daemon, the libc you run on, etc are all maintained and "fixed" and evolved by people that can barely pay for their food, even less for basic tests ?
Like i love capabilities and i would love to have more, but the basic problem here is that the low level that you totally depend on for the capabilities to work cannot even be funded to work.
Hell you do realise that Autoconf has not had a maintainer since 2012? If it was pwned and had injected backdoor in your software since then, we would have noone to fix it.