According to an episode of Acquired[0], none of Siri's original technology is present in Apple's current products. Siri originally licensed Nuance's (also an SRI spin-out company) voice recognition technology and built some pretty (comparatively) simple tech on top of it, never changing out the speech-to-text engine. All current players (Google, Amazon, etc) use neural nets, so Apple scooped up many Nuance employees…
I think the biggest problem with voice commands is that if the command doesn't work the first time, it would have been faster to simply input the command yourself. I'm not confident that "get me directions to " will actually get me those directions. Because of that, I also use Siri exclusively to set alarms (which does work every time).
I don't understand why they didn't at least add a few commands for YouTube. At least "play Band", "play Song by Band", "play Music-Genre", "play something like X", "I feel sad/happy/lonely/bored play some music".
If you want to understand the extent to which Siri is useful, you just have to look at the integration it has with the main apps. It's just Alarms, Calendar, Phone, SMS, Music, Weather and similar. It's not really groundbreaking AI, just a voiced command list to the main apps.
I am eagerly waiting for the moment when we could have more in-depth chats with our bots, but the current crop is dragging its feet when it comes even to simple commands sent to apps. Maybe they should ask the app creators to add hooks for voice commands, to make Siri more useful.
For example, if I can disgress a little, Google Now can't start playing the first video in the YouTube app on Android. If I am already in the YT app and say "OK Google, play the first track", it goes to web search instead and searches for "the first track" on the web! The same company made the chatbot, the app and the OS and they don't work well enough together. At least let users add new functions to the bot, if they can't be bothered to do it themselves.