What were the comments about Mara Jade? And what exactly was Lucas's own ideas about Luke and who said that? Did it come directly from Lucas? (If so, I'm not discounting that he's just not being nice or wanting to trash Disney for erring with Luke).
The idea that Ian McDiarmid being the surprise (?) guest at the end of the teaser isn't an example of Disney trading in nostalgia? Or the return of Lando, or just like in the other films, Luke, Han, or Leia, along with the droids and Chewbacca, or even the Millennium Falcon? Or the anthology films that went right back to the OT era? Or the First Order that for some reason unexplained on film mimics the look and feel of the Empire. Or that the Resistance members started calling themselves Rebels before TLJ was done. A lot of this is about nostalgia, and has been since TFA. If Disney had wanted to break clean from the past, they could've set the sequels 100 or more years into the future, or even went deep into the past. Disney could've easily bypassed the Skywalker Saga (and any feelings of being constricted or limited by said saga) by not simply including any of them. They could've designed totally new ships, etc. But no, they fell back on the familiar, in part because it was safe and because it has sold and was selling, at least until Disney.
I do agree with you that there is a balancing act here, between old and new, though not a balancing act with nostalgia, because the Disney films thus far are steeped in it. I can imagine that one of the reasons they've treated the OT characters so poorly is it's a sleight-of-hand move to disguise how less different or less fresh the sequel trilogy is to the Star Wars that's come before.
I do think the sequel heroes are being built up, though it doesn't appear that there's much of an overall plan in mind for them, after two films, and things were just done of the fly, but there's little consistency (couldn't think of a better word here) in the character arcs, except for Ben Solo.