How do I remove dropzone from entity browser modals?

Create a custom module. Eg:

In a mymodule.module file

use Drupal\media_library\Form\FileUploadForm;

/**
 * Implements hook_media_source_info_alter().
 *
 * - Disable dropzonejs for media library add form.
 */
function MYMODULE_media_source_info_alter(array &$sources) {
  if (!\Drupal::moduleHandler()->moduleExists('dropzonejs')) {
    return;
  }

  if (isset($sources['image'])) {
    $sources['image']['forms']['media_library_add'] = FileUploadForm::class;
  }

  if (isset($sources['video_file'])) {
    $sources['video_file']['forms']['media_library_add'] = FileUploadForm::class;
  }

  if (isset($sources['audio_file'])) {
    $sources['audio_file']['forms']['media_library_add'] = FileUploadForm::class;
  }

  if (isset($sources['file'])) {
    $sources['file']['forms']['media_library_add'] = FileUploadForm::class;
  }
}

And in a mymodule.install file

/**
 * Implements hook_install().
 */
function MYMODULE_install() {
  module_set_weight('mymodule', 50);
}

This should disable it on the normal forms. Weight 50 is just a random number I chose, it just needs to run after dropzonejs module.