Amaterasu has very limited usage. Even with the shape manipulation of blaze release, ultimately amaterasu is still only good for fights or destruction.
Shadow clone jutsu has supplementary uses (such as using clones to gather information, using them to multitask like hokage Naruto, using them to multiply your jutsus by doing something like launching 10 rasengans instead of just 1, etc) in addition to offense and defense in battle.
I'm not saying that shadow clone jutsu is stronger than amaterasu necessarily, but it is arguably more useful and versatile in its application.