There were many ways to remove Lexa from the narrative without killing her off via stray bullet. The way it was carried out in the show was (at best) lazy storytelling, and at worst it was blatantly ignorant.
Many people were simply disappointed in the meaninglessness of her death. Lexa could have died in battle, died in a climactic battle scene, or sacrificed her life for Clarke’s. It makes no sense for her arc —‘love is weakness’ and emotional suppression — to end with Lexa dying and Clarke miserable.
Season 3 had a lot of potential, and it’s sad to see that Jason Rothenberg is too self-involved to notice that he’s squandered all of his audience’s trust.