Are there times when you should give up on a particular work? Probably, if you are still learning your trade. The novice wood carver who ruins his piece of wood has to throw it away, after all.
But for someone with a proven track record to say they have writer's block is a different thing altogether. It's the job of a professional to work until you get it right. A professional should have the tools to do that, to take the synopsis and rework it into something different if the first approach didn't come out right. To take that flat, lifeless chapter and turn it sentence by sentence into something that sings.
Writing is more than just a brilliant idea. It's work, just like any other job.
Writer's block? I have no time to think about it.
Lots of other neato stuff there too. Go look.