CAD is complicated, yes. But the biggest pain point is that engineering requires a lot of adjacent knowledge about material, tolerance, mechanical design, tooling, and so on. Making things requires patience.

CAD is the easy part.

That really depends on what you're making. I've made a lot of things that are basically, I want an object with this shape, model that shape, print that shape, success. For things where tolerances and material properties matter, a little trial and error takes care of a lot of it.

There's an engineering saying that anybody can design a bridge that won't fall down, but it takes an engineer to design a bridge that just barely won't fall down. Why do you want a bridge that just barely won't fall down? Because it's a lot cheaper to build. That's not much of a concern when you're printing little doodads at home. I waste some material by designing overly-strong structures, or getting it wrong and iterating. That's fine, the stuff is cheap.