Maybe, but the lead developer is the one in charge of the software. If the community doesn't like it, they can request a change in leadership or fork the project.

> So if two people want to take "your" free software and enter an economic agreement to improve "your" free software in a way that benefits both of them, why should you have a right to say "no"?

For all the reasons mentioned above (forward-planning, insight, etc.). If someone wishes to make a change to a project, in such a way that benefits them, the project itself is never required to just accept the changes. That someone can fork the project.

Is that always the right answer? No. But it is one possibility.