If written well, love triangles can add depth and offer a new layer of tension to your main story.
A proper love triangle is three characters who are all real, deep, and who the audience will be on the edge of their seat for when the climax comes. If your audience is questioning at the end of your story if your protagonist made the “right choice”, are split between the two love interests and/or feeling bad for the one that was left out, you know your love triangle was a success. A love triangle is cliché when it’s written cliché. If your story works by adding a love triangle, then I say add it in!