Construct has a some level of 3D capability - it has depth, meshing, distort maps. It has everything you need to make a fake 3D RPG. You know Terranigma, the world view? That's all faked, no actual 3D engine. In fact, many games that seem to be 3D are faking it to some extend, as well.
You can make a Wolfenstein clone in Construct, if you just give it enough effort. It is a question of learning Construct's capabilities. Keep prototyping stuff and eventually you'll figure things out.