Lists are still functional with it - the meaning of "Go buy bread, eggs and cheese." is 100% clear. I'm sure someone has been confused by it somewhere, but it is a problem that seems to exclusively exist within debates about it.
As I noted earlier, it applies to only a specific subset of lists, those where the last two items are proceeded by a plural item that they could reasonably be a part of. So the statement "Go buy bread, eggs and cheese" doesn't apply here. (Though as I noted earlier I like to still use one for consistency). On the other hand try this list: "Go buy the groceries, eggs and cheese". When you read this it isn't immediately apparent whether the eggs and cheese is an aside (referring to the groceries) or part of the list (as in "go buy the normal groceries, as well as eggs and cheese"). It's also a problem that only occurs in writing, as your inflections in person will delineate the list for you.
Because the scenario occurs only in a small subset of lists, those with a plural item directly before the last two items in which the last two items could conceivably be included within it, the chance of a misunderstanding is small, though still existent. (I actually ran into a confusing scenario once, though an immediate query in the chat we were talking in cleared up exactly what they meant, however had it been in say a note instead of a dialogue then it would have been totally possible for me to make a mistake).
From a "speech" point of view I'd say the language as spoken certainly stands in favor of the oxford comma's use, even in cases where it wouldn't be necessary, as pointed out by SirQuiamus. If I am saying "Go buy the groceries, eggs, and cheese" where they are three separate things then I physically say "Go buy groceries *pause* eggs *pause* and cheese", as opposed to when the eggs and cheese are describing the groceries where I say "Go buy the groceries *pause* eggs and cheese".