I've noticed leftists tend to criticize gentrification on two fronts- 1- When the wealthier people move in, it prices out the longtime residents. 2- The wealthier residents move in but do not participate in the community in a way that is desirable to the longtime residents.

The economic thing I can see to some extent, but the second one ends up being hypocritical. In the mass migration debate, leftists insist that no group has a claim to any plot of land. But they throw this standard out the window when it comes to gentrification. Aside from the "right to a plot of land" problem, they also expose that they believe that a new culture moving into an area can be undesirable to the longtime residents.