> GMail doesn't have a single meaningful feature that other clients didn't have before

That's an objectively incorrect statement. It had:

1. 1GB storage when every other email provider offered like 50 MB at best

2. Superior search

3. Conversational/threaded view for emails

4. Better spam filtering

5. One of the first "dynamic" web applications to use that newfangled "AJAX" stuff to be more responsive and seem faster

Every other email provider was forced to start offering these features and now they seem commonplace. Reminds me of that old joke where someone goes to see a Shakespeare play and complains it was just one cliche after another.