inetd was designed to lazy-load daemons. while you can also lazy-load daemons like this in systemd the main points why we want the socket based activation is that we can parallelize bootup and not have to manually configure dependenciea:
we can start syslog and dbus and avahi at the exact same time, even though avahi needs both syslog and dbus, and dbus needs syslog too. because the kernel will queue the requests, and at no time the sockets will be inaccessible, and the kernel will do all the ordering for aus for free. if dbus sends something to syslog, then that data will be buffered in the kernel socket buffer and delivered only when syslog is ready to process it. and until that time dbus can already go on and do other thinga, without having to wait for syslog to startup.
syslog, dbus, avahi work with af_unix sockets, which were out-of-scope for classic inetd.
so, let me stress again: everybody who claims that systemd was about lazy-loading daemons didnt understand the idea. systemd is about utilizing the socket logic to maximize what we can parallelize, and minimize the amount of dependencies that need to be configured.
and all of this you find explained in the blog story. its just noise i have to repeat that here.