Not constructive is often the reason given when a question is subjective. SO is not meant for subjective questions. It's specifically for problems encountered while trying to accomplish some goal.

I've been on SO for a while and have a good amount of karma there. I think another site couldn't replace SO for these closed questions, (there's quora, already, anyway). There is some culture around this: you can post a subjective, or even funny question, and get away with it for a bit, depending on your reputation on the site/who you are etc. The community produces these questions and answers, so merely using a different website purposed for this case wouldn't work, since it would require the SO community to generate the content, and you wouldn't have that.