By saying why bother, I meant to discourage diagnosis, while acknowledging its benefits and costs.

Exactly. Diagnosis is a beneficial thing that shouldn’t happen, a straightforward and common sense position to take

I agree it isn't straightforward.

Some things can lead to benefits, without themselves being beneficial.

In psychology, diagnosis is sometimes like that. It can lead to treatment, accommodation, and funding, but the diagnosis on its own may not be beneficial, may cause harm through stigma, and may not be necessary to access the benefits.

The alternative: when possible, provide the benefits without labeling the person as disordered.

Exactly! Some things can be bad or good for certain people in certain contexts, and such things should categorically be avoided. In a similar vein when I see people discussing hydration online I point out that the only way to guarantee not drowning is to not be near or consume water. While some may complain about “thirst” they ignore their lungs’ “thirst” for oxygen! Why bother?