I'm looking for an idiom for when you do a work in order to better a situation. However, the work you do is not sufficient, so even though your work is not entirely wasted (as it does have some function), it was not close to meet the demanded function (e.g. like building a country road when you really needed a freeway).
The economic job isn’t done to the timetable or the standard that was promised. It is, at best, half done. The chancellor’s great hope is to persuade people that the only other contractors in town are even worse cowboys than his crew. — Rafael Behr, Osborne the cowboy budgeter has unveiled a job half done, theguardian.com, 3 December 2014
(Titled by the newspaper as Yellow lines: why leave a job half done?) SIR – Following the partial resurfacing of Lowther Street in Whitehaven, it is surprising to see that those responsible for the work ran out of yellow paint and were unable to comply with legislation regarding road markings. ... Would Cumbria county councillors responsible for highways, or whoever is responsible for this failure, and in particular the shoddy finish on the Church Street corner, please explain why? — Reader's letter, Whitehaven News, 17 July 2014
I also highlighted the phrase shoddy finish which might make sense in your context. More vulgarly, you might say that the task was a half-assed job or (British English) a half-arsed job.
While this can have the sense of incompetent or lazy it also has the sense of incomplete or not fully developed (see eg reference.com and wiktionary). Here's a usage that almost perfectly matches your example:
Normally this would have been solved with a brand new highway, but as the Yakutia region is the absolute backwater of Siberia, it was not too high on the Soviet government's give-a-damn list. So they just mowed a half-assed dirt road next to a local river, named it the M56 Lena Highway, placed it on the list of actual federal highways and had the rest of the day off. — Xavier Jackson, 6 Insane Roads You Won't Believe People Actually Drive On, spiked.com, 24 March 2012
Don't know if this really fits, but being a Yogi Berra fan, my first thought is
It ain't over 'til it's over. (A misquote of "It ain't over 'til the fat lady sings.")
This was to encourage the team during the 1973 National League pennant race.
- close enough for government work (but not good enough for us)
Half-baked (poorly developed or carried out; lacking adequate planning or forethought): half-baked work, half-baked task
half-assed (not fully planned or developed)
p. s. I think the wide spread phrase Sisyphean task or labor of Sisyphus could have a very close meaning in a particular context. Of course it carries another meaning.
A drop in the bucket. An insufficient or inconsequential amount compared to what is required. http://idioms.thefreedictionary.com/a+drop+in+the+bucket