Running grep without parameters is also pretty fucking useless.

The difference is grep is a simple tool that can take in text, transform it, and output it to a console. It operates in a powerful and easy to understand way by default (take in text and print lines in the text containing the search parameters). This vmalert tool is just an interface to another, even more complicated piece of software.

Claims to have a Unix background, doesn't RTFM.

Since when do Unix tools output 3,000 word long usage info? Even GNU tools don't even come close...

Translation: Author does not understand APIs.

The point is that these abstractions do not mesh with the rest of the system. HTTP and REST are very strange ways to accomplish IPC or networked communication on Unix when someone would normally accomplish the same thing with signals, POSIX IPC, a simpler protocol over TCP with BSD sockets, or any other thing already in the base system. It does make sense to develop things this way, though, if you're a corpo web company trying to manage ad-hoc grids of Linux systems for your own profit rather than trying to further the development of the base system.

Ok. Now give me high availability

I would hope the filesystems you use are "high availability" lol

atomic writes to sets of keys

You're right, that would be nice. Someone should put together a Plan 9 fileserver that can do that or something.

caching, access control

Plan 9 is capable of handling distributed access controls and caching (even of remote fileservers!). There's probably some Linux filesystems that can do that too.

In the end, it's not so much about specific tools that can accomplish this but that there are alternatives to the dominant way of doing things and that the humble file metaphor can still represent these concepts in a simpler and more robust way.

This reads as "I applied to the jobs and got rejected. There's nothing wrong with me, so the jobs must be broken".

This is the maybe the worst way of interpreting what they said. They can come and correct me if I'm wrong but I read that as: they have a particular ideological objection to this "cloud" ecosystem and the way it does things. It's not a lack of skill as your comment implies but rather a rejection of this way of doing things.