10 Changes That Would Have Saved The Hobbit
3. Not Diminishing Tauriel To Just A Love Interest
Jackson took a massive risk introducing a non-canon character into Tolkien's world. But the issue with Tauriel wasn't her inclusion in the story, it was the way in which she wasn't used. She's introduced in the second movie as a formidable warrior, who is respected for her skill, but dismissed for her lowly Silvan status. We're also fed the news that Legolas has a thing for her, but she doesn't reciprocate the feelings.
Already there's enough to give her a decent character arc. The problem is, non of these points are ever really explored in a meaningful way, neither is her character integral to the plot - sure, she saves Kili from the poison arrow, but that was a a scene invented to give the two characters a moment together.
Tauriel doesn't end up making a commentary on possible elven-on-elven racism, she doesn't have any impact of Legolas' character development, and she doesn't have any significant impact on the story's central conflict.
She just ends up becoming the focal point of a forced romance - that again has no impact on the plot.