There's nothing in TLJ from a pure filmmaking POV that indicates to me that Rian Johnson couldn't make a very strong original Star Wars movie with his own characters, putting aside people having their own head canon about what a character should or should not do, which wouldn't exist with new characters.
That said, he's had a huge success with Knives Out being a big hit for Lionsgate, he will have studios lining up to finance anything he wants to do, he doesn't need Star Wars or the toxic fandom that comes with it, I'd say thanks but no thanks and go take a nice $5+ million paycheque to make whatever I want somewhere else if I were him.
When you're going to be one of the most in-demand younger directors in Hollywood, who needs that headache and a 43 year old IP that's quite frankly pretty tired. You don't need that shit in your life.
