The SE ending of ROTJ provides a massive change. We see celebrations on various planets; including Coruscant, during which we are led to believe that the Empire has fallen.

In the GOUT, we merely see a small celebration on the moon of Endor. There is no reason to believe the Empire has been completely overthrown. For all we know, someone could have simply stepped into Palpatine's shoes and taken control of the remaining fleet.

EP VII could very well see a continuation of the Empire (in some form), and therefore be a follow-up to the GOUT, rather than the SE.