“Is it everything we want it to be?” Mr. de Blasio said. “No. It’s the honest goal. This is what we can tell the people of New York City can be done and can be sustained.”

The modest target and frank comments were a new tack for the mayor, who entered office in 2014 with an ambitious agenda to narrow the gap between New York’s rich and poor and to cut the number of people in the main shelter system, which was a record 53,000 people at the time.

Now, as he seeks re-election, Mr. de Blasio is shifting his focus toward moving homeless people out of hotels and so-called cluster apartments, and into more stable shelters where they can receive effective services and get on a path to permanent housing.

“It’s taken us three years to realize some of these hard truths,” he said. “There was a lot of trial and error.”

The mayor urged the public to be more compassionate, emphasizing that the vast majority of those living in shelters are families with children, not the stereotypical person on the street. He described them as Everyman riding the subway, in line at the grocery store and on the way to school and work. “They don’t wear a badge that says, ‘I’m homeless,’” he said.