The mountains are more of a problem. There is a famous Swiss village that only gets a few hours of sun in the summer because the prominence of the mountains around it is so high.
I was in the Aosta valley (on the Italian side of the Swiss border, surrounded by the highest mountains in Europe) a few weeks ago in the middle of the winter.
In short: yes there are only about 9-10 hours of daylight but it can get very bright when the sun comes out over the mountains for 3-4 hours. They also grow wine on the south facing parts of the mountains (which requires plenty of sun). And you have to consider that mountains often have clouds/rainy weather.
Another thing to consider is the peaks of the mountains are often above the cloud layers. You can get a sun burn in the middle of the winter in Switzerland quite easily. Just because it's north of most of the US, doesn't mean solar is uneconomical.
So yes, it's not optimal but there's plenty of light. And people do put solar on their roofs there and it apparently makes economical sense to them.
The population density map of Switzerland and the elevation map of Switzerland look like inverses of each other. The famous Swiss villages don’t have many people in them compared to the cities, so the situation you describe, while real, isn’t important.
In the denser parts of Switzerland, apartments are very common. I don’t see how solar works when people are living in a 5 story building. I couldn't see solar working that well where I lived in Lausanne, for example, at least on a person housed/energy unit basis.
Five floors probably isn’t too bad, thought of course that depends entirely on how many people in each apartment and how large they are — e.g. one person in a 50 m² place, divided by five floors, with 20% efficient panels, 25% duty cycle for night/latitude, still implies 500 W, compared to the average electricity consumption in Switzerland of about 900 W per person. It’s not everything but it’s also a pretty impressively large number.
(Something I only found out by looking up Swiss energy consumption: apparently Switzerland produces just over half of its current electricity from hydro power, which makes sense considering the terrain).
In short: yes there are only about 9-10 hours of daylight but it can get very bright when the sun comes out over the mountains for 3-4 hours. They also grow wine on the south facing parts of the mountains (which requires plenty of sun). And you have to consider that mountains often have clouds/rainy weather. Another thing to consider is the peaks of the mountains are often above the cloud layers. You can get a sun burn in the middle of the winter in Switzerland quite easily. Just because it's north of most of the US, doesn't mean solar is uneconomical.
So yes, it's not optimal but there's plenty of light. And people do put solar on their roofs there and it apparently makes economical sense to them.