while a western sword was like the size of a grown man and very heavy. Because of this western swords just didnt need to be that sharp.

I'm afraid these are both wrong. For a start, there's no one Western sword. There's not even, like, one sword used by professional soldiers from 15th century Germany. Some of them were going around with zweihänders (literally "two-hander"), which were straight blades and really could be 2m long and 4kg, while others at the same time were using the messer (literally "knife"), which is curved, half the length, and a quarter of the weight.

They were also absolutely kept sharp. There was little point in maintaining an absolutely razor-sharp edge because that'll just get damaged, but if it's not sharp enough to effectively cut stuff then you wasted a whole bunch of your money buying a really ineffective hammer. And you absolutely would have just used a hammer if that was what you wanted.

There were techniques for using swords as bludgeoning weapons, but these evolved as methods to counter increasingly effective armour, not because the swords weren't effective cutting tools. Holding the blade of the sword and using the crossguard as a hammer is one of the better-known examples of this. But that's something you do if you do not actually have a hammer with you and nonetheless need to fight a guy wearing plate armour. If you're carving through the four hundred peasants he brought with him, you want to cut stuff. Even against the guy in armour, rather than bludgeoning it you might prefer to hold your sword with one hand on the hilt and one halfway up the blade so that you can effectively direct the tip into the tiny gaps in the armour, at which point sharpness is very important again.

European cultures absolutely did have refined martial arts for wielding swords. We just didn't put much effort into to preserving them once guns replaced the swords.