They say the true sign of a leader is to inspire people to be leaders themselves. Another sign of true leadership is putting your team in the best position to suceed.

With that said: Core should focus on core. It should provide the hooks, docs, etc. that allow plugin devs and theme devs to suceed (read: add value to WP core.)

The mindset that core needs to be the kitchen sink is dangerous, unnecessary and dated. Ultimately, the market is VERY diverse. WP should think less about being a hammer and everything being a nail, and more about being a tool box that makes more devs more successful.

Put another way, there's a reason we have the plugin (and theme) architecture. If that's broken, then let's fix it already. Because the fact is, feature bloat has killed plenty of products.