I think that the question may be: does this particular journey "count"?
If the story is a single plot, all focussed on the final goal, does the journey either saliently advance that plot (even if through other means than the thing that the characters thought would help), or provide important character development, or bring the characters to places important for the "real" journey?
On the other hand, if the story is more a Random Events Plot, with the final goal just being a reason to be out there doing things, does the journey provide interesting things for the characters to do?
If "yes" to the above, then I think that it can potentially work: as long as the journey provided something, as long as the journey "counted", it may well not feel wasted.
My Games & Writing
Wondering if this is an acceptable application of It's the Journey That Counts...
A Ragtag Bunch of Misfits goes of to hunt a MacGuffin that they belief could defeat the Big Bad. Upon finding the stuff, they discover that the MacGuffin doesn't work, or has a side effect that they don't want to risk (e.g. it may cause an Earth-Shattering Kaboom). They end up using some completely different strategy to defeat the Big Bad.
Is that a workable plot twist?
The journey to find the MacGuffin does give the characters development, but currently the outline is such that some of the party members still has some issues that needs to be resolved before they can start working on their new plan. I'm afraid this might disrupt the flow of the story, because you would think that after the big reveal, the story would go full speed to the main action, and not meander around with more exposition about the characters' motivations and backstory.
Not to mention, It's the Journey That Counts seems to be an ending trope (or, at least, it marks ending of an arc), and I'm not sure how workable it is as a midpoint twist.