Even the existing “additional” apps (Pages, Blogs, Gallery, Downloads, Commerce) only get minor improvements every 1,5 to 2 years. IPS doesn’t have the resources to add another full-fledged app with the required functionality and if you look at which sites use Invision Community, only a fraction even has a use for an LMS. So it just doesn’t work.
I am seeing paths to possible compromises though. For example: if Pages databases were coming to Clubs, clubs could be sold or offered for free as a “course” you sign up for—with all the lessons added as Pages database records, plus course forums, course calendar and so on. It still wouldn’t have all the bells and whistles of a LMS, but it could be a good solution for many and be fully native to Invision Community.