@Tfmonkey Based on your comments about vegetables not tasting like anything (which you've made similarly about bread) you've only ever eaten store-bought or commercial-grade bread and vegetables, and in that I do include most Amish and farmer's market food.
Sourdough bread that you make yourself from ancient grains like einkorn or antique whole wheat varieties has amazing flavor just like vegetables that you grow yourself organically have excellent flavor.
@Tfmonkey
Onions: sweet mostly.
Potatoes (not Russets, but a variety like Kennebec): savory, a little bitter
Rhubarb: sweet, sour
Cabbage: umami, bitter
Carrots: sweet, savory (depending on the variety)
Parsley: savory, bitter
Swiss Chard: savory, bitter
Beets: umami, bitter, sweet (depending on the variety)
It's really hard to lump some flavors into the five categories (though I know them) because they are more nuanced, especially the aromatics like garlic and onions.
@Tfmonkey Vegetables: Umami, sweet and bitter, depending on the vegetable.
Rutabegas are sweet and umami.
Celery is bitter and savory.
Good bread is mostly umami.