This is an interesting question. WordPress.org is best for basic usage support, not development-related questions. It's easy for those to slip through the cracks.
Stack Overlfow and AdvancedWP are best for more advanced development questions.
WPQuestions.com would've been perfect, but as you said, it's been shut down. It was an interesting site, but I feel like their "downfall" was being overrun with very complex questions with like $5 bounties.
You could try here at WP Chat. We don't allow basic support questions, because those are best suited for the WordPress.org forums. But intermediate development-related questions should be fine.