We use commas to help the reader with phrasing. The Oxford comma is used in lists, and I suggest that it is sometimes helpful and sometimes not.
If the items in a list are single words, the comma creates an unnatural gap, and so does not help. I went to the shop and bought some apples, bananas, beans and pears. No advantage to inserting a comma after beans'
If the items are phrases, a comma can help. He found the argument lacking in substance, unsupproted by evidence, and internally inconsistent. Comma after evidence helps phrasing,
So, a judgement call, depending on the phrasing we want.