[asveikau]

I don't think it's just old software that might break. One must also consider the software not yet to be written. If the isolation is too constraining for some type of application that really needs a privilege, and isolation is mandatory, then some amount of innovation will just have to happen somewhere else or not at all.

Remember old school Mac was full of hacks upon hacks upon hacks, many by third parties, and there was cool stuff in there too. The App Store mentality has caused everyone to overreact and think that every third party app on the planet will turn into the worst conception of Win98 era malware overnight if unconstrained, when this is just one outcome among many possible.