Although i can agree it makes an area look nice,
gentrification raises the living cost of people who already struggle financially to make a living in the area/community, and because of the raise in living cost, they have no choice but to move out and find even cheaper neighborhoods to live in. These low cost low income neighborhoods are usually full of gangs, drugs, literally all kinds of crazy sh***. Gentrifaction literally forces the low class/poor out of their homes and into even more crappy areas or worst case scenario the streets.