Bitcoin is a technology and a network. Its preferred use has been an investment and a store of value but with layer two solutions it could also become a currency. The dollar is also volatile, but always downwards so I don’t see why a currency couldn’t have upward volatility. Bitcoin could be more than one thing, the market will decide.
Myspace is not a good analogy, they didn’t have the miners, the nodes, the network, the protocol, the investors or 200 million users. A better analogy would be the 110v american electricity network. Not the best, not the most efficient but it will stay forever because implementing a new one will be prohibitive. In 2100 electricity in the US will still be 110v. Network effects.