Double-post, but I didn't answer to the rest. About the rules, I agree. I don't understand some rules, especially at BP and Retro BC3. But it doesn't matter for me, cos that's mean they're the same rules for everybody. And videos are here to understand what's the best strat. But I recognize it's hard to understand, especially for new players.
About activity, that's easy. I already saw different polls, and MKSC is the less estimated of Mario Kart games... But honestly, the activity at this moment isn't so bad ; I saw worst.

Of course, some of your points of view (rules, ZZMT, updates on the site) can also have an influence. I'm also wondering if there aren't too much tracks ! 40, it's enormous...
About terms, I'm not bothered cos it's definitively worst at SMK.

So I think it's the same problem with all Mario Kart...
About news, I'm also not bothered. The site lives since 20 months without standards, after all !

The most important for me is AF. And Average Finish is more often updated (around once per week), so it's OK for me.