So the advantage is supposedly that it's extremely simple (just NUL-terminated JSON over a stream socket!) except that, when you look at the spec, it's actually not that simple, so they have only implemented a subset, and then they have also extended it with more features, so in the end it's not simple and not really even Varlink?

And it's now 40% slower at serialization and it can't embed binary data, but that's OK because now "web native folks" can be OS infrastructure developers without learning a new format? Except the interface definition format, which is not JSON, but for some reason the wire format has to be.

And all the D-Bus stuff, with all the problems enumerated in the presentation, will still be kept around, so we'll have D-Bus + systemd's "quite different" D-Bus variant + Varlink + systemd's Varlink variant that "does not bother with" the spec but has "additions", all at the same time.

It doesn't sound "extremely simple" to me.