For all of ROTJ's"flawts", I actually thought hooking him up with Leia was a pretty fine idea to begin with :D

The kinda cheesy way they did it "ok, you and Luke" "No, Luke is my brother" ..." ":DDD" with the cheering Ewok in the background, along with the general lack of tension and "flatness" between the two (Han had some douchey moments, but it kinda paled in comparison to ESB), was the flaw.

Would've also been better without Luke being her brother, so that the "triangle" (that was never as present in the first place) was resolved in a slightly less convenient way - Luke becomes the "traumatized spiritual leader" or something + they finally realize their feelings for each other are and have always been platonic... almost like siblings.
Kinda the same in spirit, but without the cheesy kinship.

Han could've done something more interesting and significant than planting a bomb, to round up his arc better.
But hookin' up with Leia is a nice touch in itself ;)