What are you talking about ? The Japanese stock bubble took 5 years to inflate and 12 years to reach pre-bubble levels, and that's patently clear form the graph. A similar shape can be seen for Japanese real estate, fast upside, long and drawn-out downside:



Notwithstanding, your definition of a bubble is arbitrary and wrong - the slopes of the upside/downside are irrelevant. A bubble is defined by speculative overvaluation of the fundamentals driven by herd behaviour, and we had and still have plenty of that in Bitcoin.

You can change your own definition, but that won't stop everybody else to call the bitcoin price evolution what it is: a speculative bubble.