> You only need copyright assignment for one single reason, and that's to create and sell something that contains my code but is not bound by the license.
To be fair, there are other reasons, such as keeping open the option to switch FOSS licenses down the road. I'm not saying this is the most common reason or important one - I think you are right that the commercial aspect is usually dominant in the relevant projects.
> I, as a lowly contributor, may not do that. Only the assignee can. That's a fundamental inequality, and it cannot be fixed by forking.
By forking, you take away their capability to do that - with new code in your fork. In time, your fork may become the dominant one, and you will have essentially converted the old copyright assignment project into one without copyright assignment. Exactly this may happen with MySQL and OpenOffice.
So I would say, yes, the problem you are concerned with *can* be fixed by forking, and FOSS licenses are designed exactly to allow such fixing. If they could not fix in such a way, they could not guarantee our freedoms.