I think the opposition to sushi is not because it was a food that our ancestors didn’t eat, but because it’s a symbol of secular hipster “foodie” culture, which some feel is not good for spiritual growth.
Driving in many frum jewish neighborhoods I see fancy Chanderliers and fancy Italian furniture
My issue with hemish foods is not the foods themselves, but rather the way people treat it , Like its holy or something, There is a book Ive quoted before which says one should eat Chulent for melava Malka instead of Pizza because there is something special about Chulent . If you want to eat Pizza for Melava Melka, enjoy yourself
or someone posted something before that Gefiltle had the Ta’am of Shabbos while Sushi was just fancy fish. The only reason Gefile might remind anyone of Shabbos because people rarely eat it during the week and people rarely eat Sushi on Shabbos (It doesnt refrigerate well, otherwise Id use it ). If people would eat Sushi on Shabbos, then it would have the Ta’am of Shabbos.