That's because we associate character in cities with poverty, but only in retrospect. No one likes the slum now, but everyone will miss it when its gone. On a related note, building things costs money, so new things will inherently be "richer" or "more corporate" than anything they replace. The only exception is when the government does the replacing, but while Government Center isn't very corporate I'd argue it's plenty soul-less.
FWIW, there was nothing pleasant or inviting about the blocks directly abutting Fenway Park before this started (Kenmore Square and residential areas of the Fens, yes). The few buildings that weren't cinderblock or tin shacks are mostly staying (though 109 Brookline is replacing one of them). For this project in particular, I really can't see much reason to defend this...
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Over this:
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