A coalition of Boston residents and community groups is strongly opposing Boston Mayor Michelle Wu's proposal to permit skyscrapers up to 700 feet tall in the historic downtown area of Boston. “PLAN: Downtown was meant to reimagine the heart of Boston,” the coalition wrote in the letter, a copy of which was obtained by the Boston Herald. … Boston would be better off without this destructive plan.”The BPDA board is set to vote on Thursday, Sept. 18, on the downtown zoning plan. The historic area of downtown Boston, noted in the letter, involves the residential Ladder Blocks and Park Plaza neighborhoods to the west of Washington Street and adjacent to Boston Common. Enacted in 1990, this law restricts the creation of new shadows on the Boston Common and Public Garden at certain times of the day, according to a coalition statement shared with the Boston Herald.