I think you’re right from the perspective of an individual developer. You and I are not about to fork Chromium any time soon. If you presume that forking is impractical then sure, the right to fork isn’t worth much.

But just because a single developer couldn’t do it doesn’t mean it couldn’t be done. It means nobody has organized a large enough effort yet.

For something like a browser, which is critical for security, you need both the organization and the trust. Despite frequent criticism, Mozilla (for example) is still considered pretty trustworthy in a way that an unknown developer can’t be.