Technically, Biden is correct. Every part of the Constitution, including the Amendments, can be changed by another Amendment. If you were to post this in 1925, it may seem that Prohibition, being part of the Constitution, was absolute because it was in the Constitution. Obviously, it was not.
That said, usually when this is brought up, it has to do with the First or Second Amendments, and there are plenty of exceptions to the rights they guarantee. There is such thing as unprotected speech or unlawful assembly, for example, and arch-originalist Justice Scalia famously stated in Heller that (paraphrasing) the Second Amendment does not allow any person to own any gun in any situation. The 13th Amendment even has its own built-in exception, for prisoners.
Without knowing the context, then, based on the wording alone, the statement is correct: No Amendment is absolute.