These are not system failures. But always putting players against low AC opponent is a DM failure. Encounters should be varied and challenging. By not using varied encounters and making the encounters more or less the same, the DM is encouraging players to take these feats. This is where the sense of these feats being over powered is coming from.
My players prefer to see different kind of encounters in which many styles and abilities will come into play. Always munchin against low AC, high HP opponents is not their cup of tea and it's not mine either. Not all fights are in big rooms or in the open. Some are in dense forest, others in cramped corridors, smelly swamps or even in the air! Variety makes GWM/SS not that great as they are somewhat limited in scope. Not all encounters are resolved with damage per round.
So am I. I wholeheartedly agree with you on that. Unfortunately, most of the time, the problem comes directly from a DM's bad habit or a misunderstanding of the system or a rule. It can happen to anyone. I raise my hand and say: "Guilty of that myself." That is why I come to this forum. People in here share their knowledge freely and with dignity. That is what I like. Sometimes I'm right, sometimes I'm wrong. The goal is to improve both my knowledge and my play.
No they're not system failures. They work as expected (at least in my games and many that I am aware of). But you can bet that players will find ways to make things go in unexpected ways all the time. Be it a rule, a path taken in a dungeon that bypasses all your clever traps or anything else you can think of.
Lacking originality in RPGs is quite an oxymoron. I don't think that anyone in here lacks imagination. But it can be easy for a DM to fall into bad habits or to miss the obvious. The pole itself shows that (for the moment) most people see nothing wrong in the feats themselves. Are we all wrong? I don't think so. Those who consider the feats to be over powered are concerned with some interaction. Yes, some of these interactions can make these feat truly shine. And then again that is what is expected from them. But with sufficiently varied encounters they won't dominate the field.
And to be frank, I am more afraid of Mobility, Sentinel and Alertness feats... These feats work in all circumstances and can be a real pain in the a**.