Yeah, the completion of Han's arc is the best thing to happen in the series so far IMO. ROTJ sure as shit didn't give him much to do, so count me out of the opinion that the movie gets "worse" when the "old people" come back. The Han/Kylo scene is the best scene in the series from an acting/cinematography standpoint and it wouldn't make any sense to not bring the three major characters back and finish their arcs in a more satisfying way than what ROTJ attempted. Not to mention the movie still very much focused on the new characters.
Luke was in a fine place, arc-wise at the end of VI, but Han and Leia I felt didn't really get much. TFA rectified that for Han, and it's looking to do that for Leia.