For me, the question was "Can I reduce my dependency on mobile devices by 90%?". And for me that answer was No. If all you do on your phone is reply with either "Yes" or "No" and use Siri for all other things, then yes. I found even for driving directions that my Apple Watch is just a nice to have during the drive, but I still prefer to input the destination using my phone.
I view smart watches as a convenience, but smart phones are a necessity.