Sorry, but it almost seems like some weird variation of Stockholm Syndrome that people get excited about this. It is a trivial feature that should have already been there, and was actually there over 5 years ago before they removed it. If you want to feature compare, Issues is still way behind what various other issue trackers had many years ago.
Although I'm not OP, I use Phabricator (https://www.phacility.com/phabricator/) at work and I absolutely love it. It's much better than Github for our use case, as it has subtasks, task merging, priorities, Kanban workboards etc. Tasks can block another task (for instance, the "Implement OAuth2" task can block the "Build a private API" task). You can flag objects for later and set specific privacy rules for every task (for instance, you can hide a security bug from the public until it's fixed). It's all tightly integrated with other Phabricator apps, which is a plus. Also, it's open source.
