Not really, although it's closer than other build systems. You can omit some dependencies but not all. If I remember right (I tried out tup a few months back) you still have to specify outputs, and there are some fiddly restrictions around writing files to other directories (although they were in the process of improving that).

Writing a tup build script doesn't really feel like just writing a shell script that does the thing you want. It's very cool technology and fun to play with, but I didn't find it fundamentally easier to use than other build systems.