Something of value that is worthless in the current context?

The closest phrase is probably "double-edged sword", indicating that the value is dependent on the circumstance. However, the phrase does not exactly coincide with the concept you are trying to express, because money is good in the vast majority of circumstances, while a double-edged sword implies equal benefit and harm. The adjectives "agathokakological" and "bittersweet" have similar denotations. The colloquial expression "One man's trash is another man's treasure" (indicating that something worthless in one context is valuable in another) could be reversed, forming the anti-proverb "One man's treasure is another man's trash". Additionally, the term "Midas Touch" could be reinterpreted as something that seems valuable prima facie, but in certain circumstances is deleterious (as when King Midas accidentally turned his daughter to gold). Unfortunately, there does not seem to be a word that perfectly matches that concept. I hope these related terms can be adequately substituted.

The metaphoric gist I'm getting from your question is :

"the cure is worse than the disease"

"don't throw water on a grease fire" and the related "douse the embers in gasoline"

an environmentalist friend of mine once said "they're still solving their problems with cane toads and kudzu" which made me laugh and seems totally appropriate. These were invasive species that were originally brought in to solve smaller problems than the one's they created.

What is the context or audience? A business talk and a novel would use very different language, of course.

The phrase that occurred to me was "situationally appropriate," which judging from a quick search is a big research focus of design, psychology, IT, and the legal fields.

However, I suspect that's not the connotation you were going for.

There's a whole bunch of phrases that hint at this:

• "water to a drowning man"
• "coals to Newcastle"

See this ESE entry.

For more extreme examples, a fitting phrase might be "the golden handcuffs." I first heard that in community college many years ago when an English professor mentioned that he used to be a lawyer, describing the profession as "the golden handcuffs" since he made a lot of money but had to work long, stressful hours.