First of all, people have been making diamonds out of coal and, apparently, it did not really effect the price of the stones.
Pretty much anything that's perceived as a store of value can be amply replaced by something else yet these perceptions stick around. Copper is just as shiny as gold and there is plenty of it, but my wife wants gold for some reason.
The reason for that stability is the network effect - once something has been adopted and there is a cost to moving to a new product, that product persists despite technological deficiencies. You can write a fully functional operating system for a few thousand dollars, yet Windows still rules supreme. You can probably write a replacement for the Facebook for a few hundred thousand too, yet the challenge is in attracting the users. Once one or two cryptos will become super-aggregators, the smaller ones will die no matter how superior is the technology.