Isn't that pretty much just d7 without the d7 EoL? Better to migrate a d7 site to it (assuming a rebuild with current Drupal is too much work or doesn't have necessary modules) than run d7 despite EoL, but I'm not sure it makes sense to spin up a new site using it over current Drupal.
It started off as a fork of d7 (really very early d8) but it's since diverged into it's own thing. It still has a core that is d7 compatible, so migrating is very simple (you can import a d7 database and it just works), but the theming layer is different. It's placed an emphasis on usability and modernization.
It's definitely a good choice for migrating from d7, and could also be a great choice for a new site for someone who enjoys working on a classic drupal stack.
The people behind it are great, but the community right now is kind of small.
