Why exactly should you advertise to old players? They are already usually fully informed. Can do their own houserules etc.
Maybe let the core book be a core book for newer DMs.
Maybe have some advanced book later.
Maybe when new DMs are not so new anymore.
And then in the last video I saw, they explicitely called out that the advice in the new DM might also be quite useful for old ones.
And remembering, how it was when I started playing, the first chapter should be read by us old DMs too. There are two headers in the TOC, that read: "respect for the DM/the players".
I hope that chapter gives good guidelines how the game is thought to be played together, not againt each other.