How they should've handled the she-elf Tauriel

Other than the obvious "she shouldn't have been in the movie at all", if they wanted a bad-ass female elf chick, especially to fill a quota, and have her be tied to Legolas (who shouldn't have been in the movie either), there was another less-cringe way to do it.

Instead of suddenly falling in love with the dwarf Killi, she should've been friends with Bilbo, just friends. He gets her to sympathize with him and his quest, and then she convinces Legolas to help out too. Then, during the final battle, she tries to defend Bilbo from that large orc after Bilbo gets knocked out. Legolas shows up later to help, but he's too late and sees her get killed. Legolas then kills the orc, and after being traumatized by her death, and some heartfelt words by Bilbo, Legolas is moved by how she sacrificed herself for others, despite he himself looking down on non-elves up to this point, and so he tries to be more open-minded with other races from then on.

That way, Legolas isn't cucked, he has a personal stake in The Hobbit story, and WB gets their fan-service and diversity quota without all the cringe stuff.