It was totally a cult.
However, like the word "God", the word "cult" has been de-contextualized from its origins. As far as Epicureanism goes, it checks all of the boxes. Veneration of a figure-head who is treated with reverence? Check. Small following of a subversive ideology? Check. Sayings, rituals, and celebrations according to a personality, institution, or system? Check.
Hiding abuse beneath the guise of authority? Non-existent. Punishments for non-compliance? Absolutely not. A membership fee or pyramid-scheme structure? Negative. Requirements to cut ties with family? The opposite is true.
So, just like the counter-intuitive answer this materialist has to the question of divinity (he's a theist ... just a materialist theist, contrary to modern definitions of "theism") the answer to the question of "Is Epicureanism a Cult?" is, as I see it at the moment, a resounding "Yes". However, as a "cult", it is also the total opposite of something like Scientology.