think you need to take this in context - results are what the end user will see, for sure. However, if you are making an engine, that means you are planning on re-using it on more than one project. That means that your end users will actually be other developers (or yourself if you keep it as a hobby). In that case, I would highly, highly recommend going through the exercises that you are describing here and consider different aspects and designs that you could implement.
This makes you think more about how you are doing things, gives you more and more experience with the language that the engine is written in, and helps you learn more about the API you are using. These benefits may not be tangible in the end result of a rendered frame, but they will certainly be tangible in your development experience as well as your debugging of issues during development. So I would agree with Steve that output matters, but disagree that it is the only thing you should focus on!
^ This, end result obviously matters, but if you write bad code, it makes it hard to add features to the game/engine, and it also makes it difficult to bring on new developers. Also bad code begets more bad code.