When Twitter (TWTR) reports earnings on Feb. 10, analysts will have their eyes on some important numbers beyond the top and bottom lines. Growth in monthly active users, or MAUs, for example, should give us a better idea if the service is making positive strides under CEO Jack Dorsey.

But there are some things that won't necessarily be reflected in the numbers -- and may not come up in the conference call -- that should demand investors' attention.

Some businesses had a lot to say about the platform during Digiday's annual retail summit, and it painted a bleak picture for Twitter's place in the increasingly competitive digital-advertising landscape. So bleak, in fact, that the publication referred to Twitter in a headline as the "'left-behind' platform."

Complaints about Twitters ad platform vary
In short, retailers offered a wide-ranging list of gripes about Twitter as an ad platform. "The resources and time it takes to create custom content for Twitter does not equate to the engagement and activity, so it feels like a left-behind platform," an executive of beauty products maker Haven Beauty told Digiday.

Another retailer complained there aren't enough "viable options for marketers to want to spend money with the platform." "Twitter still feels relevant as an outlet of communication; it just doesn't factor when contemplating and allocating social media dollars for a media plan," that unnamed exec told Digiday.

That complaint touches on another problem Twitter faces as it seeks to build out a better ad platform: It already allows companies to connect effectively with their customers and potential customers without having to pay a dime for advertising. Brands have been successfully building Twitter followings, and operating campaigns using the platform for some time.

If Twitter can't offer ad products that provide those companies a significant advantage over what they are already doing on the free platform -- or cannot demonstrate that its ad products offer that advantage -- it will have a tough sell on its hands.

Growing market, growing competition
These executives are saying that Twitter may be left behind at this stage in the game, and that is cause for concern. The digital ad game is about to get even more competitive.

Facebook (META -2.28%) is recording impressive growth in its ad revenue. Year-over-year revenue was up some 52% in the fourth quarter of 2015, which was reported on January 27th. The company is continuing to gain traction with its Facebook platform, especially in mobile, and it remains in the relatively early stages of monetizing its popular Instagram platform. At the same time, new entrants like Snapchat and Pinterest are commanding growing attention and ad dollars.

According to documents obtained by TechCrunch last year, Pinterest estimates that its revenue will grow from some $169 million in 2015 revenue to a whopping $2.8 billion in annual revenue by 2018. That would be twice the revenue Twitter brought in in 2014, and would be two years sooner in the development of the companies, because Twitter was founded in 2006, and Pinterest in 2010.

Meanwhile, a recent poll by Cowen & Company showed that nearly a quarter of senior ad buyers plan to start spending money with Snapchat for the first time in 2016, well more than any other platform. For comparison, just 4% of ad buyers indicated they will start spending money with Twitter this year. Because Twitter is a more-mature platform, that's not necessarily damning. But it's not good news, either.

What advertisers want to see from Twitter
The retail execs that spoke with Digiday had some advice to offer Jack Dorsey and company. The publication's "short wish list" from the retailers:

  • Better ways to understand and tap into trending topics.
  • A greater ability to make sure users are not missing tweets from people or brands they deem important just because they weren't on Twitter when they were posted.
  • A "clearer sense of what Twitter's for and why people should use it."

The first two items items on that list should have relatively easy remedies. After all, Facebook and other players already offer similar features.

The third item, however, is a much tougher fix. It goes to the heart of Twitter's identity, and the fact that retailers are bringing it up shows that, at least when it comes to brands, it has yet to establish its place in social media.

Now a decade in development, Twitter may find time running short before it truly becomes the platform that was left behind.