I totally agree that knowing how triangle/fragment clipping works at the lowest level is a valuable skill but for the vast majority of people its a level of complexity way above their need. From a practical perspective (i.e. you want to make a Game, Simulation, realtime 3D rendering of any kind), you should not be writing a software rasterizer. As an exercise in learning, go for it, but if you want to have both practical and marketable skills, you need to learn a graphics API like OpenGL, Direct3D or even Metal. These APIs mask a lot of the implementation details but in return you get a fast, reliable and consistent API.
From a high-level, you find ways to use these APIs in smart ways to optimize for modern graphics cards. That in itself is a MASSIVE challenge and not to be underestimated. This is where a smart use of API calls becomes an excellent Engine.
For myself, I started backwards, learned OpenGL then Direct3D then finally built a software rasterizer and raytracer. To me that was a great way to learn because I first understood the high-level concepts (what are textures, what is a mesh) before learning low-level concepts (what are barycentric coordinates, how does bresenhams work, how do you do perspective correction).
Just a guess.