Which ones are the best for the anglophone world currently? I'm struggling to find traditional forums that are still "alive", general enough to cover a broad spectrum and well-moderated to remove all noise.

You are missing the point by looking for a broad spectrum forum. Look for specific, niche forums, where people are interested in the topics discussed, snd not in "being a forum". Broad spectrum anything converges towards looking like social media. Naturally, avoid like a plague any "off-topic" or "politics" subforums. Unless you are in a politics forum, in which case, godspeed.