Keeping track of your tasks is a matter of bookkeeping and I’ve moved from a double-entry to a single-entry system. It also cuts the review time in half trying to decide context assignment.Summary: you didn't get rid of contexts, you adapted them to fit a form that works for you. Not so different from those who adapt them trying to put energy level etc in them.
This is, I think, part of the problem with GTD. It overloads us with silly analysis over what the next action is — “Move hand forward; Pick up pencil; Move pencil over paper; Lower tip towards paper …); or what “@Context” a given action belongs to. And so on.
To each his own: If your larger life goals are to be the quickest email-processor, bill-payer, and errand-completer that your friends and family have ever known, then by all means make sure those tasks are organised and completed with the utmost efficiency.
What GTD doesn’t acknowledge well is that the really important stuff gets done. Automatically.
Contexts are poor discriminators for deciding what to do (too many things can be done in my office, online, etc.); far more importantly, CONTEXTS ARE PLACES I GO TO IN ORDER TO EXECUTE PRIORITY ACTIONS, not the reverse.