[mgbmtl]

Composer mostly replaces 'drush make'. You can still download zip files (for core, themes and modules).

Composer helps if you have to manage complicated modules. For example, CiviCRM is CMS-agnostic and bundles its own versions of Symfony, Guzzle, etc. If we only used zip files, we would end up with library conflicts. Composer helps fix that.

(However, I agree that Drupal tends to make things insanely complicated, and the upgrade process is underwhelming.)