I've seen that quote a thousand times and I disagree with it profusely. After 30 years of it now on my part, I know we can and should do better. And that does mean reinventing it, not being resigned to the status quo.
There are 2 options: Either we incrementally improve, or we break with tradition. I'm pretty sure people have been saying that we should break with tradition and do better than unix at least since the 90s, but for just as long the incremental improvements keep coming and keep being perfectly good. Modern unix-family OSs are not the unix-family OSs of 30 years ago; we have crash-consistent filesystems, your choice of improved security systems, assorted jail/container systems for compatibility/scaling/security, better service management, etc. Or perhaps phrased differently:
> After 30 years of it now on my part, I know we can and should do better.
We are - just in place rather than throwing out a perfectly good system and ecosystem.
What usually happens is that people reinvent functionality from layer 3 at layer 47.
1. Constant weak reparsing of formats in shell pipelines.
2. Completely dangerous and unsafe API and principal programming language.
3. Trying to remember several different domain specific languages.
Apart from the fact that these days you can hardly call C principal (yes, it's still used for the Linux and BSD kernels, but quite rarely for any new userland project at all), what are your main gripes with the API? It is well understood, stable, most people know its limitations, it's being used by most servers and clients on the Internet, so I'm curious why you call it "completely dangerous and unsafe".
As for the API, the entire permissions system is just a shit show (inflexible, setgid hack, no MAC, terrible ACL implementation), ioctl (hack job), signals (totally inconsistent handling), links (hard complexity), open(2) flag craziness, then the semi userland crap particularly PAM recently and anything which involves delegated permissions from yp/nis/ldap. Urgh it's hell.
I'd rather write win32 if I'm honest these days. At least they have the honesty to break the API when it's dead by adding Ex on the end of a new one.
You might need to train yourself to ignore the ads blinking at you from your start menu and taskbar though.