"all the poor" is correct and usable in written English.
It can be used as a collective noun to refer to a group of people who are poor. For example, "All the poor deserve a chance to improve their lives."
I wanted this movie to be the key to unlocking all the poor North Koreans.
"Protectionism protects nobody, least of all the poor," he told his elite audience.
After all, the poor will always be with us, as the Good Lord said".
You see he lives with all the poor people in this room".
A part of the answer is that raging is all the poor dears can do.
I really do feel very sorry for all the poor people.
Above all, the poor lack the institutional framework which, in the West, improves decisions.
"We are trying to help all the poor people of all segments of society," she said.
If you want to see the rich kick out all the poor in a committee get read of Proposition 13.
What this country needs now is a Marshall Plan to rebuild all the poor neighborhoods in our country.
The people in Totality experienced something all the poor saps in Partiality never did and probably never will.
