Those are also all apps made by Apple. You might be able to reasonably argue that there has been degrading quality in Apple's own apps. Personally, I love Mail and don't use any of the other native apps.
I don't think that really says much about the quality of the ecosystem for developing native apps though. Some of my favorite apps are Notational Velocity, 1Password, and Sketch.
Where? I vastly prefer native OS X applications to both Windows apps and most Linux GUI apps.