"Progress" is defined differently by different people.
Gentrification is a fascinating topic to me for a variety of reasons. When a neighborhood is in a rough state, people will bemoan the current state it is in, talk about how nobody will invest in the neighborhood, etc. When the neighborhood starts to revitalize, people bemoan how it's more expensive and "different" it is than it used to be. So...what is it exactly that anti-gentrifiers want? The neighborhood to get cleaned up, but it stays dirt cheap and exactly the same as it was before? How exactly are you going to get that outcome?
Also, it's funny how nobody wants it to further gentrify once they move in. A good buddy of mine bought a house a couple years ago in a heavily gentrified part of town. There previously was no housing on this parcel of land; now there are 20-odd houses, including his. Now, right beside his house, the same developer that built his house is putting in a couple of rows of townhouses. He's pissed, thinks there are "too many" people living there now, and hates the "greedy developer." I told him there were probably a ton of people who thought that same thing when he moved in.