Was watching some "Spacedock" on Youtube, giving a quick rundown on some of the new Resistance ships. Perhaps a reason why the Raddus was used in the end for the suicide mission was because of its size. It was 3km long apparently, whereas the new First Order Star Destroyers are about 2km for perspective. The medical frigate was a new (in Universe) Nebulon C class (we have seen Nebulon B's in the OT, the medical frigate at the end of ESB) and was not very large or heavy, and same goes for the final ship we saw destroyed. Some sort of Correllian model that is apparently referred to as a "glass cannon", lots of weaponry but very light in construction.
https://www.youtube.com/watch?v=HKWrKPEhu1k