The repeated folding reduces the carbon content which is why Japanese smiths started with “pig iron”. What you end up with is still fairly good steel.
The end product is probably fine. I’m sure the Japanese Smiths had fine products in their day. That’s not debateable.
It’s just that the more time you have to fold the metal, the less products you can create. I suspect that European swords were cheaper to make because they could output more swords. If I had to buy a sword in Europe or Japan, given a choice, I’d probably buy a European sword for that reason.