It's worth saying something with real value can still have a bubble - both bicycles and the internet were huge market bubbles at one time, but they're also undeniably valuable.
Let's assume bitcoin has a tiny but positive probability of running the world economy in, say, 50 years. Ie bitcoin is a lottery ticket.
The fair value for a lottery ticket is some positive number. In 99.99..% of cases, the ticket will expire worthless. (In 0.00..1% of cases it will be worth quadrillions.)
The fair value of a lottery ticket is not a bubble, even if most lottery tickets expire worthless.
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Now, of course, it's still possible to overpay for lottery tickets. Eg if you buy an actual lottery ticket in retail, the whole transaction usually loses you at least 50 cents on the dollar for lottery taxes alone.
But that's a separate issue.
Lottery tickets were only an example.
Also, I gotta say I do not think Bitcoin is a bubble or whatever (IMO a real value there), but really this sort of site makes it seem like it is a bubble with the sort of "blind to history" boosterism.
Go read Reminiscences of a Stock Operator, or Market Wizards series, Extraordinary Popular Delusions and the Madness of Crowds, or any number of books about financial history and there are endless people saying 'it will never die and all the doubters are just wrong' before any big market crash.