RAMALLAH—When the Trump administration reveals its economic plan for the West Bank and Gaza this month, it hopes to appeal to Palestinians like Amr Marouf, who manages a seafood restaurant here.

Saying his people’s “future is dark,” Mr. Marouf, 27 years old, has all but given up on a Palestinian state alongside Israel, an idea that has for decades animated international efforts to resolve the Israeli-Palestinian conflict.

“Maybe...