Prices can move within a certain range over a relatively long period of time. But that doesn't mean that the price of bitcoin will forever be within that range. One day the price will definitely leave these numbers. Price stability is something that will be hard to happen in decentralized things where no one can control it.
Being decentralized is not the core reason why bitcoin is not having stable prices. Being volatile maybe due to decentralized system but bitcoin is having fluctuating prices as it is still in its early days and yet valued to its maximum level but that will take more time as no one could predict what will be the demand when all the bitcoin will be mined out. Bitcoin was designed to have fluctuating prices and definitely not to have a stable price. This is because only fluctuating prices will be attracting more new people to get into adopt it. Yes, bitcoin needs lots of new adopters so that it will hit mainstream.
Since Crypto is one of the most volatile assets ever, I don't think you will see anything "stable" for a long long time.
Yes, it may take a century of time to have stable prices for bitcoin. I'm not talking about for all cryptos in general but it is true with respect to bitcoin as it is having limited and predetermined supply but no one could predict the level of demands of future. Hence, we cannot expect a stable price in any near future.