I love Sun Valley and ski there annually so I'll take a shot. First, you are absolutely correct that it does not get a lot of snow traditionally and it tends to have a lot of its terrain groomed. If that is an disqualifier for you, don't fight it and just figure that Sun Valley is not for you. You will not be alone in that camp.
Second, I would disagree with your statement that it is not the place to be in tough seasons as Sun Valley is able to provide what it provides as consistently as anywhere in the country. I live in Utah and am a Snowbasin season ticket holder (which has allowed me to set number of free days at Sun Valley for the past 5-7 years and at a discount rate prior to that time). Our annual trip to Sun Valley has been over Martin Luther King Jr. weekend in January for 4 out of the past 5 years. Sun Valley has skied consistently well during that period every year even including 2 years ago when large portions of Utah were struggling to get significant portions of their terrain open. Sure, skiing was significantly better this year with softer snow and a couple of 5-7 inch powder days on our trip. So I think Sun Valley has consistency dialed about as well as anywhere--the question is whether that experience is for you.
Third, it is a misconception that Sun Valley only has groomers as it has large bowl area, interesting tree skiing, and a fair amount of quality mogul skiing. However, long, consistently pitched groomed runs are a huge strength and Sun Valley's calling card. If you don't think 3,000 of uninterrupted vertical on a fairly consistently pitched run is interesting then; again, you are not its target audience. In fairness and even as a fan of the place, I often ski the sides of the big boulevard runs or the numerous gully runs for a little terrain variation when skiing there. At the lower end, the mountain is much steeper than the norm and you will not find steeper "beginner" (green circle) runs anywhere. At the upper end, the black diamond runs are generally pretty steep but not like the most difficult runs at Jackson, Snowbird etc. By the way, Sun Valley is serviced by one of the most efficient and least crowded lift systems in the country. You can log more vertical in a shorter time at Sun Valley than any other place I have skied. Park skiers and beginners have their own hill across town at Dollar Mountain (my kids often want to spend a few hours there each day in the park).
Finally, the town and the overall feeling are intangibles that have a very real and positive impact on the experience. My family has several restaurants that we have to visit every year. Perhaps our feelings would be different if we didn't ski every weekend and were counting on Sun Valley to tick all the boxes on our one annual ski trip. However, as it is, it is a trip my whole family looks forward to every year.
As a postscript, my two older sons and I went on a weekend ski trip to Jackson two weeks after our trip to Sun Valley. Jackson is another mountain we ski on a near annual basis and we had absolutely primo conditions with lots of deep powder and lightly cut crud runs the whole time we were there. While we were driving home from that trip and even in the face of the epic weekend, my oldest son still held true to his preference for Sun Valley over Jackson (but more along the lines of picking out which supermodel you prefer). While I prefer Jackson as a ski hill, I prefer Sun Valley/Ketchum as a town.
