Content, terms and user/author import or migration to D8 without custom module
I have successfully migrated D7 content into a D8 site with similar content types using this small drush extension for D8 along with the built-in D8 Upgrade option:
https://www.drupal.org/project/migrate_upgrade

I believe the upgrade process from D7 or D6 is now apart of D8.3+ in the Admin UI and can simply be enabled after drupal 8 installation under the Module listing. Alternatively, you can use Drush via the module above.

Your D8 project just need localhost access to your old site files (such as images,pdfs, etc ... your old Files directory in Drupal 7/6) and database connection access.

It's a rather painless process for simple websites.

Please review the official documentation on performing a drupal 8 upgrade migration