judging from when Bitcoin was launched way back in Jan,3rd 2009 till date 2024 that's roughly about 15years of existence. If a project would fail it would fail long time ago so, you don't need a soothsayer to tell you we are unstoppable.
A project can be alive for 20 years and still fail. How old Bitcoin is and how much it has flourished isn't reason enough to determine why it won't fail. Saying Bitcoin won't fail because of how long it has succeeded doesn't do Bitcoin justice. Bitcoin has succeeded for so long because of its features.
The value of every currency, asset, or commodity is determined by the demand and supply of that asset or commodity. There are other factors like cost of production and all, but it all boils down to demand and supply. If there is no demand for that particular asset or currency, the value would be reduced. If there is a high demand and the supply is way higher than the demand, then the value would drop because one thing that increases value is scarcity. Bitcoin checks all these boxes.
One thing Bitcoin has over fiat and altcoins is its limited supply. The market cannot be flooded with billions of bitcoin just as it is with other cryptocurrencies. Going back to excess supply, that's why most altcoins aren't worth shit, but they have a high market cap. Flooding the market with a particular coin removes scarcity and when something is not scarce, it has no value.
Another feature that makes Bitcoin unstoppable is its decentralised nature. No centralised or particular entity owns it. It's owned and controlled by the people in the market. This way no particular person is responsible for adding value to Bitcoin online shares. This creates room for demand and supply to function freely.
These are just two main reasons I believe Bitcoin won't fail.