There is no reason for a tool to implicitly access my mounted cloud drive directory and browser cookies data.
Linux people are very resistant to this, but the future is going to be sandboxed iOS style apps. Not because OS vendors want to control what apps do, but because users do. If the FOSS community continues to ignore proper security sandboxing and distribution of end user applications, then it will just end up entirely centralised in one of the big tech companies, as it already is on iOS and macOS by Apple.
So when it's all said and done, I do not expect practical levels of actual isolation to be that great.