The module system is actually what I was talking about. You don't need to understand every single contributed module to understand how the whole system works. I'd like to see your example of how/where Drupal "falls apart" when adding contributed modules.
If you're writing a module when you don't understand how modules work, you're gonna have a bad time. The Examples for Developers[1] module probably would have helped out. The Field example creates a custom field. The Node example create a custom node type. Or you could have just created the node type using the Field UI (and if you need it in code, export the configuration using Features[2]).