For at least some of the all-important (to advertisers) millennial users, that may well be the case. Jacob Shiansky, 24, who was visiting Manhattan from South Carolina, told me this week that he couldn’t remember his Twitter password and hasn’t visited the site in six months.

“It’s too much business and political promotions rather than a social media site,” he said. “If you want to see Trump’s ridiculous tweets, you can go on Facebook or CNN. You don’t have to bother with Twitter.”

He said his friends feel the same way. “It’s all Facebook, Instagram and Snapchat,” he said. “They’re quick and they’re fun. You don’t have to waste your time typing.”

I can’t say my own Twitter use has been all that prolific, even though I sometimes use it to comment on my column and to recommend stories by other journalists. But I’ve stopped following some people who spew what seems a constant stream of drivel. Days go by when I don’t look at the site.

User engagement has become an increasingly important metric for advertisers, because it enhances ad exposure and gives the site more information about its users, enabling it to target ads better.

On that front, Twitter is a clear laggard. Users spent an average of nine minutes a day on all of Yahoo’s sites, two minutes on LinkedIn and just one minute on Twitter, according to recent data from comScore. Facebook reported last quarter that its users were spending, on average, 50 minutes a day.

“We regularly survey advertisers and ask them to rank internet platforms,” Mr. Mahaney, of RBC Capital Markets, said. “Google ranks first, Facebook second and Twitter is somewhere down the list. That’s been true for every survey,” he said.