In terms of fans, the gist of what's canon and what's not is this, based on how I interpret things
- Episodes 1-9
- Anthology Movies
- The Clone Wars animations (TV series and shorts)
- Rebels
- Any books post-Disney purchase
- Any comics post-Disney purchase
- Any games post-Disney purchase
So any books or comics post-Disney purchase are officially canon. Anything pre-Disney purchase are essentially considered "Star Wars Legends," formerly Expanded Universe. However, I'd say the exception therein is anything the filmmakers or story groups want to pull from existing EU which they want to be canon will be canon.
I try not to worry about it too much though because now that we are talking over 40 years of stories and material, there are bound to be contradictions and things that don't fit here and there.
I mean look how many times DC and Marvel retcon or streamline continuity in similar timeframes.
For example, as far as we know, Shadows of the Empire is a Legends book. But I imagine if Pablo Hidalgo said, "The book happened. Everything written in the book still happened." Then yeah it essentially gets grandfathered in. That's hypothetical.
So Rian Johnson just basically grandfathered in The Jedi Path.