Inetd, the software people mysteriously re-invent every decade or so

And then you don't have dependencies anymore, so you're back to square one.

I don't see how this is supposed to be more comprehensible or even "simpler" than a 12 lines unit file.

Several dozen unit files whose dependencies need not be listed in the files themselves, you mean. Which is why it's a step backwards in terms of simplicity.

You get the dependencies just like you do with any other socket activation. Web request starts the web server, which connects to and starts the application server, which connects to and starts the data store.

> Several dozen unit files whose dependencies need not be listed in the files themselves

Where else would you expect to declare the dependencies other than the file which defines the service? That's where I would expect to find (and add) the dependencies.

> You get the dependencies just like you do with any other socket activation. Web request starts the web server, which connects to and starts the application server, which connects to and starts the data store.

Fair enough!

But dependencies can also be expressed by the location of a symlink