Please don't take the Amazon star rating too serious - every lens has its pros and cons that I wouldn't want to squeeze into a single one-dimensional figure...
A quick note about me: I have been into SLR cameras and lenses for more than 20 years - as a hobby in the beginning and professionally later. Maybe because of my technical background I started testing my own lenses quite a while ago. I have a (no longer so) little test lab of my own where I do 6 different image quality tests (after taking a lens out for a while).
The AF 70-300mm F/4-5.6 Di LD MACRO 1:2 is one of the lowest cost lenses available. It's made of plastics but looks nice and feels pretty solid. It has a very popular focal range but no image stabilizer which is problematic if you'd like to use the long end of the focal range without a tripod. The lens is compatible with both APS-C and full frame type cameras (the effective focal length with APS-C is 112 mm to 480 mm) and has a macro mode that allows close-ups at a magnification of up to 0.50 x. When considering image quality the AF 70-300mm F/4-5.6 Di LD MACRO 1:2 has its ups and downs. The focal plane is straight as it should be (no "curvature") and corner shadows ("vignetting") are minor. Distortion is well under control but only if the lens is set to 70 mm and that's also where the lens is most capable of producing sharp images. At other focal lengthes it requires high f-stops to gain sharpness. Another obvious weakness of this lens are the color fringes ("chromatic aberrations") that occur both in sharp parts of the image ("transverse CA") and in out-of-focus parts of the image ("axial CA").
Though the AF 70-300mm F/4-5.6 Di LD MACRO 1:2 certainly doesn't excel at image quality it's not totally bad or unuseable and I've seen lenses that are a lot worse and cost much more. So you'd definitely not buy this lens for its image quality but to extend your focal range at an acceptable image quality, a compact size and a very affordable price.
A much more detailed review of this lens together with all test shots, sample images and technical data is available on my website LensTests_com.