A lot of people seem to take pride in not liking love triangles.
Romantic relationships are exclusive in a way friendships are not, making them way riper for conflict. Romantic competition and angst is infinitely variable but universally relatable. Most people make hard choices about when to leave or stay in relationships that define them, a love triangle is often the simplest way to distill the identity issues of a lifetime to one thematic choice.
We see this in classic literature:
Pride and Prejudice: Wickham represents the appearance of goodness, Darcy the substance, Elizabeth must learn to discern between them.
Jane Eyre: Mr. Rochester is the messy entanglement with real love and lust behind it, St.John is the perfect-on-paper partner with no physical connection, Jane chooses her own needs and herself as a whole messy person, after years of denying and repressing herself.
Twilight: Edward represents the moral restraint and material rewards of adulthood, Jacob is the safety and familiarity of planting yourself in adolescence, Bella is coming of age.
YES TWILIGHT IS CLASSIC LITERATURE DON'T @ ME.
Because well done love triangles are so successful when tied to a choice of identity for the character, the trope of two competing love interests has been thrown in and used less thoughtfully. New bad boy vs. childhood sweetheart does not have the same resonance. It has been used badly enough that it has developed a terrible reputation.
But when it's done well can be absolutely transcendent. It's all in the execution.