More engagement increases loyalty (or retention), at least that’s the myth.
Community has less influence over retention than almost any other benefit.
Price, product, promotion, people, processes and a dozen other factors have a bigger impact.
There are plenty of companies with thriving communities shrinking away when better or cheaper products emerged (Dell, BestBuy, Barnes and Noble etc…)
Part of the problem is the people most likely to join a community are already your most loyal customers. You might move that by a percentage point or two, but it’s extremely hard. Even if you succeed, it’s difficult to prove causation.
I’d look around for another benefit. Advocacy, customer support, ideas implemented, tickets reduced, SEO traffic, generating leads, reduced costs, and almost any other benefit here works better.
Your work becomes far more enjoyable when you’re working towards something you can directly influence and easily prove.