Specific to London but there were a lot of working class home owners who bought under the right to buy schenlme who have benefited hugely from gentrification (not just from increased home prices but from lower crime, better schools etc).

Also a lot of non-market housing being rented, all those people also benefit.

Sure a small percentage of displaced people benefit significantly. That’s offset by those who simply see higher rent then get forced to relocate to a less desirable location further from work / family/ etc.

Poor areas have few people with the knowledge/ resources to really leverage gentrification which is why they are living in poorer neighborhoods to begin with. So the average outcome may be a slight improvement due to the major winners, but the median outcome is likely a net loss.

The people who move in and out aren't just shuffling seats. They may be moving in because of their increased ability to exercise that position in society. The consequence may be a center of regional productivity and true national gain. In other words, you don't get a Bay Area unless a lot of tech and business types mingle together.