TLJ is different to me not because of its plot choices but thematically. Its substance, outside of the superficial tropes and rearranged story beats, is incongruous with the rest of the franchise.
There are a bunch of core themes about good and evil, heroism, and redemption, that were essentially the heart guiding the past two trilogies. TLJ goes around to challenge those, and comments on the meta-narrative of the old stories rather than try to continue them.
It’s not different because of what happens in it. I mean, to an extent it makes unexpected choices, but it still borrows plot elements.
What makes it new is how it’s not beholden to what came before and isn’t particularly interested in setting up what comes after. It’s entirely character/theme driven, and the things it explores isn’t even trying to be classic SW.