In Downtown Seattle, all the good spots on Pike, Pine, 4th, 5th, and 6th are full. Retailers are always talking about moving in "if they could find a spot". Our last big Downtown retail construction binge was in the late 90s, including Pacific Place (the size of Denver's Pavilions but on less land), Nordstrom's relocation to the giant former Frederick's store, and conversion of the old small Nordstrom into multiple stores with offices above.
The Pike Place Market, with its 200 shops and 250 daily craftsperson booths, is doing fine. I won't get into other Downtown retail districts but they're doing well also -- the furniture district along Western, the galleries and rugs of Pioneer Square, the funky stuff on upper Pike/Pine, First and Second in Belltown, etc.
As for supermarket-based Downtown projects, Whole Foods just opened with 20 other stores at the 2200 Westlake condo/hotel project (ps, 2201, an office and condo project aka Enso, broke ground yesterday!), a big QFC is part of the Lumen Condo project topped out at 5th N & Mercer, and a boutique market (tbd) is planned for the topped-out 8th & Madison apartment project.
Redevelopment of the existing 10-acre Goodwill site near Downtown at Dearborn & Rainier will apparently include a couple big box stores including a Home Depot and Target, or something like that. Plus 560 housing units, other stores, and a new Goodwill.
As for "malls", seemingly every existing mall is adding more retail space on former parking lots, and adding new garages to replace the parking -- Bellevue Square, Southcenter, U Village, Northgate, Alderwood, Totem Lake, etc. Also, new retail-focused centers are being built with denser, walkable mixed-use concepts (a sliding scale!) -- Kent Station, Redmond Town Center, The Landing in Renton, Woodinville Wine Village, etc.
Every three days it seems, another suburban city advertises an RFP for developers to develop a new mixed-use "downtown" on a vacant site, or on the edge of an existing downtown, or even on multiple properties. Retail is always a big part, housing is pretty universal, and many include new city halls and libraries. Some of these are already getting built. Examples (various stages) include Kenmore, Burien, Puyallup, Lakewood, Auburn, Federal Way, Everett's Snohomish Riverfront, and Everett's Port Gardner Wharf.
Existing suburban downtowns and urban mixed-use districts are mostly developing at a fast pace, because our region has chosen to focus growth there. This includes in-town districts like Ballard, Admiral, Fremont, Greenlake, etc., and suburban downtowns like Mercer Island, Kent, and Kirkland. These always include a fair amount of new retail but not as the main focus.
Old downtowns in Tacoma and Bremerton, both ghost towns a decade ago, are undergoing astonishing transformations. But the retail in both is still mostly just enough to serve the people there for other things.
Downtown Bellevue, where last-week's 20-story apartment start was met with a ho-hum since it's one of 16 towers u-c, is seeing a fair amount of new retail, but aside from the last sidewalk-focused expansion of Bellevue Square and the new Lincoln Square there's not much going up except a new Safeway that's part of a 360-unit apartment (woodframe, not a tower), and the two-tower first phase of Washington Square will apparently have a boutique supermarket.