It's just too spread out to deal with the hassle of such a desolate parking lot and walk down the plaza.
And now has 2 large vacant spaces with Bed Bath & Beyond and OfficeMax closed. The north end of Gateway has always been the big underperformer. And if Wynn builds a footbridge right onto HD's/Costco's/Target's doorstep they become super easy to reach from Broadway and Alford. Once MassDOT replaces the bridges on 16 over the train tracks and river widen the sidewalks it'll be easier still to get there from Wellington by foot/bike. And Costco is coming off a huge fiscal year, so I doubt they've got a rationale for closing locations.
The HD Assembly is so crushed by traffic being the #1 location in the state for contractor pickups that they truly do need the one across the river to relieve the load.
That would make little sense as those are far and away the busiest tenants there.