let people experiment, youll learn the necessary math concepts behind things doing it, and not everyone wants to make a completely 3D games. adding mode 7 type effects spices up your 2d games and in anycase isnt very complicated to do at all. getting collisions and graphics importing to work in 3d for a 2d game is much less intuitive than using construct, and construct wasnt "intended" for anything, its simply a tool to make things easier, and well to be frank i find writing about 7 events to do this is alot simpler than learning java, learning how to import 3d models and do uv mapping ect. its simple 3d, which construct is made for.
Mode 7 and what not is fine but people want to make construct into a 3d engine which it is not. if you want to add some 3d to your game to make it look better that is fine too but what I dont get is why people want to make true 3d games with construct when just to get something rendering in 3d would take for ever. Where as with unity its as simple as going into max or maya making your object and dragging it into the program and boom its there, and yes you might have to fiddle around with uvs or something other things, but its better than needing 45 events to get 1 3d model working. If your really interested in making a true 3d game you need to use the tools suited for the job, not ones that require overly complicated things to get 1 model working.
and as for not beign complicated you your self said it was not easy, and it looks pretty complicated.