The Keep It Simple 1 d4 book uses 1 d4 2 Nf3 3 g3 4 Bg2 5 0-0, and then 6 c4 most of the time. The move order avoids a few black defenses. And it's systematic, no? But there are exceptions. 6 c4 isn't always played, depending on what black has done. And if black plays a quick ....c5 the move order is derailed. The author covers the exceptions.
There is no one system opening that is good against everything black plays, white needs to adapt at times.
Isn’t that a Catalan transposed?
You avoid most variations of the open Catalan, all that QGA stuff, some Queen's Gambit lines, the ...Ba6 Queen's Indians... plus many more.
It is a sound approach which cuts down the material to be learned a lot, but I am not sure that it is suitable for low/intermediate players: Those Catalan / Fianchetto systems require subtle positional handling, and after playing competitive chess for almost 50 years I still have not seen one player of that league to handle a Catalan ending properly (truth be told, I was also mishandling them quite badly while rated 2200+ FIDE).
The Keep It Simple 1 d4 book uses 1 d4 2 Nf3 3 g3 4 Bg2 5 0-0, and then 6 c4 most of the time. The move order avoids a few black defenses. And it's systematic, no? But there are exceptions. 6 c4 isn't always played, depending on what black has done. And if black plays a quick ....c5 the move order is derailed. The author covers the exceptions.
There is no one system opening that is good against everything black plays, white needs to adapt at times.
Isn’t that a Catalan transposed?
Depends on what black plays. If black plays the setup...d5 ...nf6 ...e6 ...Be7 ...0-0 it becomes a Catalan.