It seems to me the other way around. I am a high volume user and I have relied on Gmail for almost 10 years. I signed up for inbox (because I am always looking for something better). I found it slowed me down. It was pretty but superficial. I prefer the plain but functional Gmail. Just one data point, I realize.

Thank you for clarifying. It makes the last sentence of the article make sense, but I think one would have to already know the difference between GMail and Inbox in order to understand the article with confidence.