“Mobile first” is more about progressive enhancement and making important design hierarchy decisions than it is about thinking about small screens, so I don’t agree with the “outdated” bit in Paul Adams’s Why ‘mobile first’ may already be outdated. That said, he makes a good point about enterprise software:

Many businesses being advised to go all in on mobile screens, should consider how often they are accessed while people are at work. Software that people probably shouldn’t, but do, look at on their work computer: news, sports, social, messaging, personal email. The large screen matters.

Now imagine that you actually build software specifically for people to use at work. This may be software for getting work done, such as Google Docs, Intercom, Slack, Basecamp, Trello, etc. The likelihood now is that the larger screen is the most important one. The large screen app is more important than the mobile app. The mobile app plays a different role to the large screen app, and in many cases a supporting role.

I see this is in our user research all the time. If we do usability testing on our mobile apps, one of the first questions is always, “Will I be able to use this on my desktop”? For software that gets used mostly at work, focusing on desktop — as unsexy as it might sound — is still hugely important.