To answer that question, you need to know what a pyramid scheme really is: a business model that recruits members by promising them payment or rewards for enrolling others into it.

Bitcoin is NOT a pyramid scheme, as there is no reward for buying tokens. There have been, however, platforms that used Bitcoin in their scams, but that changes nothing about the coin itself. After all, the US dollar is not a pyramid scheme, although it is often used in many of those!