I have to agree with the OP. If Linux OS going to be for mainstream users, it will eventually succumb to the same issues that plague proprietary OSes. Like low configurability (gnome is already doing this). Mainstream users want very different things from a computer than we do. And in many cases they don't even want a computer anymore, they'll just use their phone or iPad for everything.

I also don't think the mainstream really care about privacy and control. Most of them are really happy in their walled gardens. As a power user I don't want to 'dumb down' my experience and work towards that, so if they really want it they'll have to buy it from a vendor that does it for them. Most of the big names are trying to get there already (like canonical)

And yes eventually a company will make another walled garden based on Linux but it will suck because of the vendor lock-in, limited access to its internals ("because otherwise we can't support it"), and commercial to subscription services. Basically this is exactly what ChromeOS is already.

Personally I just think that a Linux that's for everyone is simply not Linux as we know and love it anymore.