I took a look into regional, northern and Canadian flying.
YEG will be very well served this summer season but a few gaps remain.
In Northern Alberta, Peace River and Bonnyville have not resumed after covid. Both places have populations of about 6,000 and are not well-served by other airports. For comparison YEG already serves High Level pop. 3,922.
In other areas of Alberta, we need regional service to Lethbridge (pop. 123,847), and Medicine Hat (pop. 67,376), and possibly Lloydminster (pop. 31, 582).
In British Columbia, YEG has surprisingly good reach but a few gaps, and some of the existing service is only seasonal. YEG should push for regional service to Ft. St. John (pop. 28,729 and within YEG's traditional NW catchment), possibly Cranbrook (pop. 27,040), Williams Lake (pop. 23,608), and Prince Rupert (pop. 13,442, but strategically important).
For northern routes, YEG has good reach with nonstop or same plane service to almost all population centres. YEG could benefit from same plane service to Fort Simpson, NWT (pop. 1,100), or upgrade existing same plane service to nonstop to Hay River, NWT (pop. 3,169), Inuvik, NWT (pop. 3,137), Fort Smith, NWT (pop. 2,248), Rankin Inlet, Nunavut (pop. 2,975), or Cambridge Bay, Nunavut (pop. 1,760), although this would sidestep Canadian North's Yellowknife hub so probably not a practical option. YEG is missing nonstop service to Iqaluit (pop. 7,429), this would be a relatively long flight, but be the feather in YEG's cap for northern service. Other areas of focus: YEG needs some carrier to resume Anchorage, and it would be great if the Whitehorse flight went nonstop both ways.
Ontario is very well served from the major and medium sized cities, with the notable exception of Windsor (pop. 422,630).
In Nova Scotia, longstanding Halifax service would be complemented with service to the tourist-friendly Cape Breton (Sydney) (pop. 98,318) on a seasonal 1x or 2x weekly basis, although the runway might not be long enough for a 737.
In New Brunswick, the new service to Moncton (pop. 157,717) would be complemented with service to Saint John (pop. 130,613) and/or Fredericton (pop. 108,610).
Service to Quebec is reasonably strong with Quebec City (pop. 839,311) starting this summer and longstanding Montreal service from a few different carriers. The other population centres in Quebec would be difficult to viably serve nonstop.
In summary, there remain opportunities for regional growth (north, Alberta, BC), and of course strengthening all existing routes to major centres through more frequency or larger aircraft.