I think it's time to give core its own place in the forum. It could be one sub category under smartapps. Or it could be its own category altogether. But it's a very high percentage of the postings now, and people just don't want to deal with threads that are 1500 post long.
My own suggestion would be to take Smartapps, which currently confuses people significantly, and add the following subcategories to it:
Smart Home Monitor
Other Marketplace Smartapps
How do I? (just rename the current "smartApp ideas" to this)
Then you can leave everything else in the existing categories.