I'm not sure I'm getting it? is UASF another version of SegWit that could (and should) be activated right away without the need of miners signalling it? If yes, then wouldn't that be the exact definition of "centralization"?
There is a huge movement and development in the bitcoin industry. The community was flooded by the fighting of greedy miners competing with its other as to whom will the control over the bitcoin production will go to. But the users, exchanges and the economic players are tired of this debates and fights as it is the money of the players, holders and investors are at stake. Thus Super UASF was born and this time as a revolution against the miners. With UASF the one to decide what changes are going to take place in the bitcoin code are the economic players and not the miners.