Hi! Looks like a good start to me. I'm not familiar with the tutorial, so I'm unsure how you made your height map - but that's what I'd edit to fix continental shelf issues. I'd mask out the sea region, then start adding various Screen layers of transparent gray, tossing it into Wilbur and doing some erosion until I got a result i was happy with. There's loads of bathymetric maps out there to be inspired by. NASA even has real-world height maps available for you to cut and paste from. https://visibleearth.nasa.gov/view.php?id=73963

I assume the washed out desert color is on its own layer. To make it less washed out, you can use Levels, Curves or Hue/Saturation (or all three) to tweak it until you get a color you like.

I can recommend Mbartlesm's mountain tutorial as well, to add some valleys to your mountains.

-Niels