OP does make a few interesting points, but I have to disagree with a lot of it. PHPBB has a ton of potential, but it leaves that up to the administrator. You get the bare bones and add to it as your needs grow. Xenforo gives you everything all at once, whether you need it or not. Is Xenforo more feature-rich out of the box? Sure. But PHPBB doesn't clutter you with bloatware. You get a forum, a bulletin board with just enough to serve the purpose of a bulletin board. But then you also get the large community of developers who are actively working on extensions for it. Xenforo's market isn't nearly as large, so while it has more bells and whistles initially, it's not the easiest platform to expand without reaching into your wallet to pay for custom work. With PHPBB, if you can think of a feature, it most likely exists; if it doesn't, you can request the feature to be made, at no cost to you. That's what makes PHPBB worth it to me.
That being said, there are some things that I think should be part of the core package, but they've already been mentioned in the ideas section. Things will continue to progress as they always have, and I'll continue to support PHPBB as it expands and evolves.