It's true that Imgur has to grow its product now to something bigger. I won't even give them many years if they don't do that for a product that simple and ephemeral. They have challenges here.
The parasite metaphor does not include the idea of being a "copy-cat"; parasites in the real world do not do the same things as their host. Indeed, that is the entire point of a parasite, in some sense; to take advantage of the host setting up various expensive systems to survive and just using them instead of developing their own.