As mentioned in the post "Of course we would have preferred it if the solution would have been perfect, but at least we had the chance to give it a try"...
When you fall you've failed at walking. But we all know that this is part of learning to walk. We can focus on the fail or on the process or learning. You obviously only see the fail.
Failure is not just a setback. A doctor has no problem saying if a child failed to learn X by Y age there may be a problem. That said there are ranges of failure, and handing money back to investors before you completely run out is a better option than running a company into the ground with nothing to show for it.