I love forums, but I mostly use Discord, Slack etc. instead these days because they're usually easier to get engagement on (presumably because they're familiar and people get to use the same platform they use for everything else). I still see a long-term need for forum software though, as the third party systems are not always the perfect tool for the job.

I think part of the reason for lack of engagement from the community directly with bbPress though, is simply a lack of need. Most of the core features of bbPress are there and functional. In my experience, it's just a matter of install and forget. There are little theme related features, but much of the extra stuff you'd want to add, are directly related with WordPress, not bbPress. Even basic registration/login stuff is a WordPress thing, not a bbPress thing these days.