I’d argue that Melee is overall the weakest class, but it does have a decent tradeoff for being bad against bosses: being the best class for exploring and invasions. Many Melee weapons are designed for invasions, like Flails or the Death Sickle or the Paladin’s Hammer or the North Pole or you name it. And it’s great for exploring because the weapons are spammable and take no resource management. You also have a lot of survivability, and even if defense doesn’t make that much of a difference you also get damage reduction and life regen later on, and profit more from stacking defensive accessories. Still the weakest class overall, but I don’t think it’s by as big a margin as most people think.
You’ll appreciate Melee’s variety a lot more if you ignore the hundreds of clutter weapons like ore swords. There aren’t weapons quite like the North Pole, Horseman’s Blade, Flairon, Combat Wrench, Shadowflame Knife etc. I could probably name a unique and decently strong melee weapon at each tier.