Its a step up for them compared to Haiti. The ones stranded in Cuba trying to get to the US probably found it a step up to. At least it’s a bit organized in Cuba.
Overall, the same can be said of any country in the Americas when you are the poorest, most disorganized, and most unlucky of countries. For example, several countries on the Central American isthmus are poorer than the DR but richer than Haiti (actually, I think all countries except Panama and maybe Costa Rica are poorer thsn the DR, but all are richer thsn Haiti.) A Haitian can go to any of them and it will not be long they notice is in a better position than Haiti.
It's also relevant for Haitians if the slums in other countries are better, often not by much than those in Haiti. Many Haitians will end up moving to those places at first, because few of them would be able to move directly even to areas with a majority population of lower middle class and up, which are the sectors that have the greatest increases of living standards compared to Haiti.
This graph, now old (data from 2005-ish and 2007-ish) is of the percentage of the population that at then lived in slums. Notice where Haiti was relative to all other countries.
Basically, Haiti was a country where most of the urban population lived in slums and now that percentage has probably gone up. With the exceptuon of places like Venezuela and at various rates, I think it has gone down in most countries shown there. Others probably are about the same.
This doesn't take into account the standard of living in the slums, because not all slums are created equal. Some get better service than others and this too is different from country to country. The quality of other things such as public health care is also not accounted for.