But here many apps follow this exact model of a list of projects which I think is an implementation rooted in paper based system. I call this idea of a single list of projects "heavyweight". The action of making a project here provides some mental resistance. You ask yourself, "Do I really want to make a project for this thing that requires 2 steps?" Unless a project feels big enough you find yourself resisting making projects. Just making projects hierarchical would at least let you bury those smaller tasks instead of having all equally visible.
There are other systems where a project is no big deal. It is just a task with sub-tasks. There is much less mental resistance to creating projects here. Some examples are Smthngs and MLO where projects are easier.
I still think someday we will have the "one" GTD app. Still waiting for it and someday may write it myself.