You are talking about Bitcoin and cryptocurrencies being a bubble for so long, but I am not quite sure what you actually mean by that. What is your definition of a bubble?
For me a bubble means a rapid drop in price with no recovery after that. A good example would be Bitconnect or any other ponzi scheme.
Bitcoin had many major drops in price in the past. Were that all bubbles that popped? If so, we will see many more bitcoin bubbles in the years to come.
For me personally bitcoin being a bubble means the following: Bitcoin can never live up to the expectation of investors and speculators. There will be no mass adoption. There will be no one using bitcoin as a store of value. There will be no one using bitcoin as an alternative method of payment all over the world. If that happens, then it is a bubble.
Are you convinced that bitcoin wont succeed in the longrun? I think it has a decent chance and definitely a way bigger chance than any other coin today.
For now Bitcoin is only useful as a pool of liquidity. When it has no such use, it may not succeed at all. Its way worse as payment option compared to many other coins and it already lost more than 50% as a store of value.