If you knew Arabic, you would know that "Qaeda" as a word has strong insinuations of structure and hierarchy. It is in the name,

For most of people, it's no more than a product of their imagination.

You've believed that nonsense. People can lie, you know.

I know people that bumped into quite a lot of salafist organizations that would later affiliate with Al Qaeda, they were well organized and had funding as well as structure and hierarchy.

In any case, a few dozen angry disenfranchised seminary students with a leader as well as en executive council and multiple branches is more of an organization than Antifa is. I know that Al Qaeda has declined a lot, but I know for a fact that it was much more than what you claim it is at least at the time.