No it's not! :@ If you hire a plumber to fix a leak and they end up flooding the room in the process, you don't say "oh that's ok, I couldn't do better".
If their aim was to produce a usable car, and they end up with only 1.2 km/l then they have screwed up.
You can't go shouting at schools kids at science fairs for failing to do something great, but you absolutely can if professionals are set a task and come up with lousy results.
I kind of agree. But I think it's on a case by case thing. But usually I just ridicule the person and pretend in my mind that I could do much better if I wanted to.