While Xiang Lu is not a good person I still think he's the best option.As koalasplayground.com(LYF translator) well said

"...not because Tushan Jing isn't a wonderful guy who is a good fit for Xiaoyao, it's just that someone else may be an even better fit that's never going to be explored."

It seems that she can settle for any of the two guys(Tushan Jing or Xiang Lu) given that they only have to focus on her, but XL can't hence that, and so he may never be fully explored as her lover.Though I am not overlooking his evil doings but none of these nobles are saints so they can have each other.

And I find Tushan Jing too perfect. Like let's be real, 'I torture you and you forgive me since your stepmother never loved you'. And nothing is ever his fault, it's just icks me. Why can't they just say that he's an angel who fell in love.