Yep, it has failed as a peer to peer cash. It's still a payment system, but yeah, the volatility. There are other assets that have actually done a much better job at doing what Bitcoin was supposed to do like Litecoin and Monero, and still keeping the POW consensus which is the strongest due to being backed by actual industrial fundamentals via equipment, power, etc. Most proof of stake chains are completely hosted on services like AWS, very few people self-host servers like that. Hell most of Hive and Hive-Engine witnesses are on Privex or something like Hetzner, or even AWS, which create major central points of failure. That's why I feel like this is what gives PoW tokens more value over PoS, and is why Bitcoin is still seen as the 'digital gold' by wall street. And it's that industrial cost factor that also drives the price up with the block reward reduction. Same premise as with gold miners and selling their gold. They basically set the spot price. The more it costs to pull it out of the ground, the more they are going to want to sell it for, same with Bitcoin, and Wall Street knows this.
BTW, I completely agree here, just bringing some different perspective in the comments, lol.
I'll add Bitcoin Cash in addition to Litecoin & Monero