The one that leaps to mind immediately is silphium which is now believed to have been extinct due to a combination of changing climate and massive overharvesting.

People generally don't stop eating dishes unless something actively prevents them from doing so, like what they eat becoming extinct. A wide range of foods simply evolved as time advanced and new cultures adopted them or new ingredients became more widely available. Many modern dishes are often heavily modified versions of what was eaten generations ago.

Other foods tend to fall out of favor simply because they're not really that good and people found alternatives that were better. For instance there was a lot of dishes made in the Middle Ages that revolved around the fact that there were times when people had to work around the church's dietary laws, which could be quite arcane. A lot of "food X made to look like food Y because you aren't allowed to eat food Y today" and some of the creations (though clever) sound absolutely revolting; I recall reading one recipe that suggested using a mixture of lard and crushed berries as a tart filling if there was a "no dairy" fast day or you were short on cream or milk (there's a lot more about this in a book by (I think) Melitta Weiss Adamson, "Food in Medieval Times").

So for the most we still eat most of what we used to eat we just eat it in different ways. Adapting an L5R quote, "If it’s got four legs and isn’t a table, if it swims in the water and isn’t a boat, if it flies and it isn’t a kite—people will eat it.”

This differs from the examples you gave in that it's a finished product rather than a raw material, as it were, but garum was a fermented fish sauce that was utterly ubiquitous as a condiment in Ancient Rome and has no significant equivalents in modern Europe.

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