I am surprised by the statement "Today, salmon sushi is a staple of Japanese cuisine"
While in Japan a few years ago, I found no salmon on the menu in sushi places.
When inquiring why, we were told that salmon is not that good, and that is more a food for kids than adults. Did it change or are we just one data point?
I'm trying to recall right now, and maybe the only places where I didn't find salmon in any of my visits was in the more expensive/ fine dinning places (think ¥8000+ places). All the common kaiten sushi places, or chains like SushiZanmai have all kinds of salmon pieces. Different levels of fat, broiled, rolls...
Is it maybe a bit more like "comfort food", for kids, for less delicate palates, cheaper? Maybe. But truth is I haven't asked why I haven't seen it in the expensive places.
It's hard to say, depending on how far back your idea of "a few years ago" might be or where exactly you ate. After all, Japan has a lot of sushi restaurants and even different sushi styles. For example, you definitely wouldn't find salmon in an edomae sushi restaurant.
For reference, salmon was the most popular choice in conveyor belt sushi places 3 years ago. https://www.nippon.com/en/japan-data/h01627/
Ah, interesting stats, specially the second part when they say what type of sushi they refrain from eating. I guess that ōtoro and chūtoro is due to price. And uni... Maybe because of the flavor? It can be a bit of an acquired taste...
I remember asking a Japanese chef in Japan, in 2019, and the answer I got was that sushi is much less popular in Japan than believed outside of Japan, and a lot more people eat rice and chicken, pork, etc., than salmon.