I hate these dumbass discussions. A sword is a sword, they have different shapes for different purposes and are good at different things, you can't just compare stats and call one outright better like a video game. Euros in fact had quite a few weapons with similar shapes designed for similar combat roles.

Throughout history, other than the big two handers, swords were generally sidearms. Samurai were traditionally horse archers, against armored opponents(other samurai) they relied on heavy warbows or lances(and later matchlock guns), and when they did fight on foot at close range they generally did it with polearms because reach is king. Katanas are excellent for slashing unarmored/light armored foot soldiers from horseback as a backup to your bow/lance, and for carrying around day to day to face unarmored assailants like robbers and assassins. They were not good at piercing armor because they weren't MEANT for piercing armour, they had reinforced polearms, clubs, and heavy duty daggers(pic related) for that. Katanas also had some issues with fragility but thats not because of the design its because of Japan having low quality iron. Also "piercing" plate armor is a nonsensical myth, you're supposed to jam it into gaps which a place where a straight sword has an advantage.

A sword is a sword and the katana was perfectly fine at filling its niche. My only complaint is that for regular day to day carry swords they were a bit long, but that was more of a tradition thing.