> There are so many times the Oxford comma prevents ambiguity. I have yet to see a counterexample.

In every counterexample that I have seen the ambiguity involves an appositive phrase set off by commas which is lurking nearby in the sentence.

Commas are the most common way to set off an appositive phrases but most sources say that em dashes and parenthesis are also acceptable.

This means you can use a simple rule and not have to worry about ambiguous lists: (1) always use the Oxford comma, and (2) if you need to set off an appositive phrase for an item in the list set it off with em dashes or parenthesis.