Hello, Q2A developer here.
1. I can't speak for everyone else, but I've been incredibly busy with paid work so I've had very little time to do any development and discussion in the past few months. But I should have more time soon!
In terms of the community, be the change you want to see. Get involved where you can, answer questions, make plugins, help report & fix bugs, improve documentation, etc.
2. Actually it is. MVC means Model-View-Controller, it's a paradigm regarding separating of concerns. Q2A separates those concerns pretty well - the controllers are separate (in qa-include/pages/), the various functions are separated and categorised fairly well, and views/theming is separate from all that. I'm not saying Q2A does it perfectly, but it pretty much follows the definition.
You may be talking about using OOP (Object-Oriented Programming). And it's true, Q2A falls down here. But I'm slowly migrating the codebase to a more modern format while trying to keep backwards compatibility where possible.
3. The next version (1.8) has taken some big steps forwards in performance, but it's always been pretty fast anyway in my experience. If you're having problems please post some specifics and I'll see what I can do to help.