Notice there now are options like "Move to", which basically removes the tag for the current folder - I mean tag - and applied a new tag to let people treat Gmail mostly as if it is folder based, because as it turns out a lot of us insists on folders. But that functionality didn't use to be there. Both the nesting and "acts almost like folders" actions were added at some point long after Gmail was launched.
In this latter case the gmail model is great. I leave everything in the inbox and depend on gmail (a) never to lose it and (b) to find it easily through search. In fact you can use gmail as a doc store--if there's something I really value I make it an email attachment and depend on gmail to dig it up if necessary.
I'm not sure if I agree. I think it might be better to software to excel in one specific workflow rather than attempt to cater everyone. Of course this requires the market to provide different options for different workflows.
I don't leave everything in the inbox for the reason that I can't find what I want, in part because the search is awful. A large part of the problem is that unlike websites where pagerank and context provided by inbound links allow a lot of intelligence, with my e-mail it is often a struggle to find the right search terms, and so I want to add context in the forms of categorisation to the messages I actually have a reason to keep.
Gmails poor folder support kept me from using it for my work account for many years, until they "surrendered" from their original hardline tagging stance and added more support to allow you to treat tags like hierarchical folders, for this reason.
I can't imagine keeping an unstructured inbox like what you're describing - I wouldn't find a thing. I always despair when I have to resort to Gmails search as it almost invariably means I'm in for frustration.