Yes, even if the GTK+ file browser is three orders of magnitude slower I'd rather use it.
Don't get me wrong, I would be happy to see whatever bug is causing that performance difference
fixed but it's just not a problem for me in practice so I won't be the one submitting the
patches. I spend at most a fraction of a percent of my time at the computer using the file
browser and I believe that's true for most people. Optimizing it in just one application at
the expense of a consistent user interface is a poor trade.
As for listening to customers, you're implication that free software projects don't is
mistaken. They do, but there are too many users with too many requests to satisfy everyone,
just as there are for successful proprietary products. Available resources are spent
according to what seems to be most important. You clearly have a different idea of what's
important than GTK+ and Mozilla developers but this alone doesn't prove that they're wrong.