It's easy to find fault, to discourage, to critique. It takes no skills, hardly any effort, and it comes naturally to almost everyone. What's worse, it actually is somewhat satisfying to point out someone's faults- I know every time I have in the past, it's made me feel wise and intelligent.
Finding solutions to a problem and then actually carrying out a plan of attack is a completely different ball game- it's hard work, requires skill and insight, and takes dedication. And it's far more satisfying in the end.