Rian Johnson was hanging around for a ton of production and post production on TFA and had a bunch of really in-depth conversations with JJ about the direction of the story. Hell, I seem to remember JJ even saying Johnson asked him to tweak a couple things so they would lead into his movie more smoothly, and JJ’s already read his Episode VIII script and presumably given feedback on it. This is not JJ and Kasdan turning around after their movie and saying “screw you guys, you’re on your own”, it’s simply someone else getting into the driver’s seat to keep it fresh. The LFL story group isn’t flying blind.