IMO the title is incorrect because the common interpretation of getting "burned out" is that of the same individuals of a population losing effectiveness after working hard. The article even likens the term "exhausted" the same interpretation of the phrase:

Altogether, our research suggests that T cells in tumors are not necessarily working hard and getting exhausted. Rather, they are blocked right from the start.

This same quote describes the truth of the phenomenon where it's not individuals getting "exhausted", but cellular signalling permanently altering the expression of T cells to make them less and less effective.

A more correct title would be something like:

Cancer makes every generation of T cells worse than the last