Twitter (NYSE:TWTR) made some changes to its ad products at the beginning of the year that have gone on to negatively impact its revenue growth throughout 2017. By cutting its underperforming ad products, Twitter was supposed to be able to focus on the performance of what was left over and make them more attractive to marketers. But that doesn't appear to be the case.

Earlier this month, RBC Capital's Mark Mahaney said Twitter, along with Snap (NYSE:SNAP), came out weakest in its semi-annual marketers survey. Twenty-one percent of marketers said they plan to decrease the amount they spend on Twitter.

Meanwhile, Aegis's Victor Anthony says his conversations with marketers indicate a similar sentiment. He said one advertiser told him "Twitter's management has not quite made the case for shifting meaningful ad dollars to Twitter."

The social network faces tough competition from Snap, Facebook (NASDAQ:FB), and Alphabet's Google, among others.

Exterior of Twitter HQ at night.

Image source: Twitter, Copyright Aaron Durand (@everydaydude) for Twitter, Inc.

Twitter users aren't engaged

Twitter's struggles to grow its user base have been well documented. Additionally, it has struggled to keep users engaged on the platform. Twitter, in fact, officially won't provide any engagement details, like its daily active user total, or average time spent on the platform per user. The SEC even questioned Twitter's practice of only offering year-over-year growth in daily active users instead of actual numbers, and Twitter still wouldn't budge.

Management let slip last year how bad it is at keeping users to stick around, while trying to boast about how many people actually use its service each year. Based on management's comments last year, around 20% of its users may be completely new, or recently reactivated accounts every month, which is offset by about 20% leaving the service every month.

Twitter's reluctance to provide any engagement data stands in stark contrast to Snap, Facebook, and Google. Facebook says its users spend an average of more than 50 minutes per day across Facebook, Instagram, and Messenger. Instagram users under 25 spend an average of 32 minutes per day in the app now, while those over 25 spend 24 minutes per day with the app.

Snapchat exhibits similarly strong engagement, with those under 25 spending over 40 minutes per day in the app. The average user spends over 30 minutes per day.

Google recently reported its YouTube viewers spend over 1 hour per day streaming videos on mobile alone.

You know how they say, "If you don't have anything good to say, don't say anything at all?" Twitter's management has been very quiet when it comes to its user engagement.

Poor engagement means poor advertising performance

Not only does limited engagement mean advertisers have fewer opportunities to present their messages, it means the messages that users see are often less effective than on other platforms.

Big-brand advertisers, which make up the majority of Twitter's ad revenue, derive value from their advertisements through repeated exposure. If users aren't frequently logging in and spending time on Twitter, they won't get exposed to a message enough for it to work effectively.

On the other end of the spectrum, small direct-response advertisers benefit from highly targeted ads that are more likely to convert viewers into buyers. But without significant engagement, Twitter's ad-targeting data is lacking compared to Facebook or Google's. As a result, both sets of advertisers are seeing lower returns on investment compared to competing ad platforms.

Twitter has tried to boost ad engagements through several measures over the last couple of years, but none have seemed to provide any positive impact for marketers. While ad engagements climbed significantly, the increase was offset by lower average ad prices. Twitter's average ad prices have fallen for eight straight quarters.

Considering that there are several growing platforms with better engagement and targeting options, advertisers can do better than to give their money to Twitter. Until Twitter solves its engagement problem, it will continue to struggle to attract advertisers' budgets.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.