Word/phrase for "treating the problem rather than the symptom"?

Solution 1:

Root cause refers to the fundamental reason for the occurrence of a problem.

As Wikipedia describes it: A root cause is an initiating cause of a causal chain which leads to an outcome or effect of interest.

Another way of saying this, in more formal terms is ultimate cause, which is essentially the same as root cause. The complement of ultimate cause is proximate cause, (sometimes used as a legal expression) which is the cause closest to the problem. For example: "The proximate cause of his diabetes is that he is overweight. The ultimate cause is that he does not eat a balanced diet."

Solution 2:

In a medical register, the difference would be between "curative" (problem oriented) work and "palliative" (symptom oriented) work.

E.g.: "The social reforms leading to the state administration of old-age pensions were a palliative effort to prevent the rise of socialism." and "The reorganization of the company was meant as curative; Apple would be in the tank, otherwise."

Solution 3:

“Avoid palliative solutions, and treat etiologically.”

It may sound too fancy for some, but I do believe that that's the perfect and concise expression that summarizes the whole message, including its details. “Tackle root causes” is a common expression, but it does not also call for dropping the “painkillers”, does not intelligently deter from going for palliative solutions; instead, the expression above invites the reader or listener to consider what a painkiller really is and what it does, then also concisely tells them that sometimes you cannot just “tackle” a root cause; you may have to research and study it, practice etiology.