I've been "playing with" (using - but not in a work sense) Drupal on-and-off for over 12+ years. I've installed it many many times and played with the various commonly used modules, but rarely doing much with it. Aspirations, mainly. Drupal 6 was probably the version if got most used to (and, as of December 2018, still have a tiny long-standing site still running it). Since 2014 I've managed a Drupal 7 site which was an evolution, but managed much the same way -- uploading files from the release zip to the hosting provider, trying to remember any library dependancies.
In other words, I've got to 2018 without having to figure out Composer.
Now that D8 finally has decent media/image modules available in core (or "near" core) I finally want to move the D6 & D7 sites to D8. And Composer now seems unavoidable. Adding to that, I want to do development on Drupal VM, which also encourages Composer.
Some best practices..