SW can be seen as completely detached from the other 8. It was the only one made without the ideas of the saga in place, and it shows. It really does stand alone and I can never watch it without getting the feeling that the story could well have been over at the end of it.
Lucas can say what he wants, I don’t see his 6 part saga as about “The Tragedy of Darth Vader”, but I get that, original film aside, it is a way one could see it. I’m not at all that bummed that the ST “trumped” that understanding, though. Thematically, however, I think the ST kind of falls short. It has one movie that left something to be desired (TFA) one movie that tried giving it all meaning through beautiful character studies and journeys (TLJ) and ??? (TROS), so depending on my mood, the Star Wars saga is either one movie long, three movies long, six movies long or seven movies long, with TLJ serving as an epilogue.
But then again, I think the question of the thread was already answered with great mastery by NFBisms and DominicCobb a couple pages back.
Back when I used to marathon the PT and OT, it always felt like Eps 4 and 5 just didn’t fit. ROTJ did, for me at least, seem to be in the same universe as the PT.
So when I saw TROS (with very little in the way of expectations) I was very surprised to note that it felt like a natural successor to TESB. It was as if I’d quit Star Wars in general after 1980, ignored the movies in between, and then caved and gone to see TROS. So my head-canon goes 4,5 and 9 - ridiculous as that may sound! I have to say though, if TESB wasn’t so damn brilliant I’d be a 'Star Wars ‘77 only’ guy for sure.