Yes, even moreso now since it hurts your Google page rank to not make your app mobile friendly.

I believe it only hurts your google rank for searches conducted on a mobile device.

So, most searches, then.

In 2015, my primary use of web apps "for mobile" is to find the link that says "full site".

That's exactly why the inverted advice needs to be heeded, so that that sucky experience, which does still occur daily with a lot of sites and apps, goes away by default.

Note, I'm absolutely not saying that a big screen desktop experience isn't inherently better for all but the simplest apps, there's very high probability it is because it's more ergonomic hardware with far more screen real estate.

However since most people want to, and do use mobile in preference to desktop for a huge proportion of tasks now, the design philosophy in most cases needs to flip from 'full functionality for desktop, scale down gracefully for mobile' to 'full functionality for mobile, scale up for desktop, taking advantage of the extra UX potential where possible'.

It's actually a far more optimistic, and creative, approach. Make it, then enhance it for the less popular use case rather than make it, then degrade it for the less popular use case.