The characters shouldn't all be related
I don't care if it's supposedly the story of the Skywalker family. It doesn't need to be. I can accept Darth Vader as Luke's father. Leia as his sister was a stretch, but ok. Then we find out Kylo is Han and Leia's son! I'm sure Rey will be Luke's daughter, or some other Skywalker. It makes the story ridiculous.
Episodes 7-9 should have had a non-Skywalker villain with an interesting (and fully explained) background.