Divide and conquer
> the ability to freely modify whatever software is running on his computer and share it
This ideal is great for the tiny minority of highly able individuals who have both the skills, motivation and the time to do this. So far as making Linux (or other GPL projects) popular, accepted and used by ordinary people, it's completely irrelevant. A theoretical nirvana that (even more than free speech) is promoted by its ignorant or naive proponents as being something it is not - and never, ever could be.
So while a small number of geeks can take a project and fork it, they are simply diluting the brand, A few forks turn out to be more successful than the original vision and yet more forks take over from dead, dying or stalled projects. However most of them offer nothing different or innovative but are merely platforms for someone's ego. (exactly how many MP3 players or DVD rippers does one universe need?).
What this means is that the GPL world is like an undisciplined army - a horde of separate proud footsoldiers, who take orders from no-one, rushing headlong with their battle-cry of "software wants to be free" towards the organised and fatally disciplined ranks of professional software developers. Sure: the GPL-ites may have numbers on their side, even enthusisam too - but superior marketing, design processes, documentation, training and support (albeit paid for) is no match for the unwashed marauders who's doom is inevitable - even if they happen to be right.
So instead of GPL software being a directed force. Applied to fixing the problems that everyday users want fixed and supplying a free, ubiquitous, easy to use, flexible solution that would be universally adopted at low cost and without borders we have a balkanised, unstable source of software. Instead of being usable by "the average person" it requires enormous, duplicated effort by each individual who wishes to install some of its parts - usually requiring a whole load of other dependent parts, too.
What will be GPL's epitaph? Instead of a headstone, reading "We made software for everyone to use", there will be a series of tiny pebbles with poorly spelled inscriptions scratched on them - mostly the same, that when put together will read: A Lo'st oporrtinity LOL"