This grade comes only from the lack of consistency. There are AMAZING dorms at Northeastern, but there are also super old god-awful dorms. So, I can't give a totally high or totally low grade because it all depends on where you live!
The freshman Honors housing, International Village is swanky. I had a single that had a connecting bathroom to ONE other girl. We had a gym in our building, a bamboo garden outside on our floor, and a huge laundry room down the hall. I was the second person to ever live in my room. There are also really nice dorms in the West Villages. These 7 buildings (A-H, except D (??)) all have really nice upperclassmen options from 3 single-bedroom suites, to 3-double bedroom suites and everything in between.
There are also utter disasters. Since Northeastern is an urban campus growing at a ridiculously fast rate, it has apartment buildings that it leases out and manages for its students. This option means that the level of care to these converted apartments is often lower, and the fact that they weren't built as DORMS makes the experience much less positive for a lot of students. There are also some REALLY old dorms that aren't in great shape. Thankfully, there is tiered pricing for housing based on building, so if you're on a budget, you can accomodate those needs too!
So, overall, considering that there are about 30 residence buildings at Northeastern, the condition of on-campus living is pretty good! There are a few weak links, but there are PLENTY of options, so you should be able to find a dorm with the combination of amenities, location, and price that suits you!