I think it's only really depressing if an advancement is stuck idly behind something non-technical like lack of capital, or legal wrangling, or being acquired and shelved. Other than that, if there were real technical bumps that sidelined the advancement, well that's just part of the process.

What one really wonders at, is technology where there were technical failures, but were really a small distance away from success for lack of combination the right bit of information to push it over the edge - but are now locked away in storage in some proprietary corner somewhere.