Well, the Maine Med and Public Market sky bridges were designed to bring people from a parking garage to a set location without having to cross a busy street that didn't have any ground-floor appeal to begin with. At least here it appears meant to generate more viable retail space on the 2nd floor of the Wharf Street building, which would otherwise end up as office or residential space. There is also existing ground floor retail up and down Wharf Street that will continue to provide foot traffic.
Honestly, it's not my favorite part of the design, but I don't see this destroying the street life at all on Wharf Street. I think you're still going to get the foot traffic coming up from Commercial Street and from the far end of Wharf Street. If anything it might cut down on foot traffic coming down from Free Street, but hopefully they can use the interior design of the 2nd floor of the Wharf Street building to then funnel foot traffic down to ground floor on Wharf Street with a grand open staircase or something. The masses have less of an issue going down stairs compared to going up stairs.
Maybe they could get rid of the diagonal cross members and make it all glass, if structurally possible? I think that would be more appealing.