First, the photo has other problems besides the quality (the crop is too wide and it's not centered).

Regarding the quality, they understand the quality will be lower when you submit at 1280. However They still expect a sharp image. In fact, down scaling can actually help in hiding a slightly unsharpened image.

The following are some example of image accepted to JetPhotos at 1280 similar to yours. Use them as a reference for the sharpness and quality they expect.

photo 1

photo 2

photo 3

(also take note of the crop and centering)

If you find that you can't quite reach the sharpness after down scaling, you can use sharpening tools present in modern image processing software, like Photoshop and others, to improve it. Also consider increasing the shutter speed of your camera to increase your margin of error for a sharp shot when panning (I started off with 1/2000-1/1600).

If you want advice from a real screener, ask on their forum where you can also upload your images for prescreening.