(The discussion coming relies on visibility of the number of chairs ahead of you on one of the high speed (wider spaced) lifts.)
It can be. My opinion is it depends on how fast the lakes freeze. Best case we get a real cold snap early on and it stays cold enough to keep Whitefish Lake especially frozen. Flathead Lake is way bigger and I am not sure if it ever freezes completely, but last year Whitefish Lake froze early. So I don't think there was a single day I skied last season that wasn't two chair or better. (That's my personal indicator of "maybe I should go home", when it's zero to one chair.). Now, is two chair okay for you? Maybe not. I've grown into it. Three probably is. Two maybe not.
In a bad year (both prior seasons), the lake never completely froze. I had my first ever zero chair days, maybe two or three days each of those seasons. And a fair amount of one and two chair as well. I was pretty exhausted by it after a while. You know, one day a week, that's all I wanted.
So, it depends on the season and the TIMING of the lakes freezing. Because they are big enough to not freeze over night, it takes sustained cold.
Now, all that being said, I think on average it's roughly 25% of the time, over the course of an average season, that it's foggy. I ski roughly 70 days a season, without regard when I leave the house to the weather. I have my schedule and rarely alter it unless the R word is definite. I may leave the hill early, but that's a separate topic. And the reason I don't pay attention much to the weather before I leave is, in spite of the fact that my house is only 2 miles from the summit as the eagle flies, and the base is a mere 800 (?) feet higher than my house, it's a different micro climate up there. In fact, each little zone up there is different. So, until you get there, you don't know what kind of day it'll be.
Whether the fog is an issue for you will largely depend on your skiing ability and the age of your eyes. It doesn't bother my daughter one bit. She's in the trees anyway. And she's got young eyes. And "Ya ski with your feet, Mom, not your eyeballs!". When you live here, you know the areas to avoid on bad days (you won't find me on Toni Matt or Inspo, that's for sure). You learn to stay closer to the trees on the side of the trail, even if you're not in them. You learn that for foggy days, you don't want freshly fallen untracked stuff, you want it cut up so you can see texture and slope better. You learn that Chair Two is usually UNDER the fog layer. Stuff like that. Not unlike skiing in the Spring. You use your knowledge of slope aspect to judge when things will be softening and what areas will still have dry snow, not slush or ice. Or your knowledge of prevailing winds to know where the snow is skiing deeper instead of being blown off.
The payoff is the fog keeps the crowds away. And, ultimately, the prices down.