It's core product is git hosting, you use it to host your git repositories. You use features such as Pull Requests to power how you merge within your git repositories. If the issue system isn't working it's not a big deal, but if we can't use git it's a massive deal. It's all in the name GIThub
Most companies don't use GitHub's issue management system they use issue management tools such as JIRA, Trello, etc. Issue management, project management, CI/Actions, wiki, discussions, etc are all nice to haves and are probably more aimed at the open source projects that are used as a marketing tool.
