If you've been building Drupal sites for a while, you know the pattern: a new requirement comes in, you reach for a custom or dust off an aging contributed module, and before long your code base is a patchwork of narrowly-focused solutions. Over time, maintenance becomes a chore.
There's a better way.
Drupal 8 introduced the plugin system — a big leap toward modularity. Suddenly, we could write small, focused classes to add functionality in a clean, reusable way: