Gentrification is a problem because it flows from historical discrimination, and the power dynamics tend to fall along those lines.
If everyone had equal wealth, or if wealth really were distributed according to merit, gentrification might just be some unpleasant but necessary feature of changing economies, labor markets, and urban life.
But instead what we have in the United States is a society where some groups have been robbed of wealth generation after generation, and others have been gifted that wealth and allowed to inherit it instead. So even if most de jure racism either is no longer on the books or can’t be openly enforced, we still have the equivalent of grandfather clauses operating all over the place.