If you believe in the occult magic can be both mystical and require physical objects to work and have physical effects.

Before ROTJ the magic of the Force was like magic in Buffy (a hidden mystical knowledge that with training and the right aptitude can turn anyone into a powerful sorceror).

ROTJ made it more like Harry Potter (blood lines etc).

The PT explained some of how the heredity stuff worked with fantasy science.

This is a significant loss to the series, that sense that it could have been you in that x-wing cockpit.

Luke is just some ordinary kid from the middle of nowhere in the first film.

By ROTJ he is the offspring of royalty and pure blood wizard.

It's like Doctor Who, back in the sixties and seventies kids could imagine that the Tardis might land outside their house and the Doctor might take them on an amazing adventure.

Now 'contemporary Earth' is a fantasy realm where everyone knows that Daleks are real and London/Cardiff gets blown up by aliens every Christmas. It places hurdles in front of that immediate suspension of belief leaving ROTJ and the PT a less awe-inspiring place.