It doesn't really matter who you put the blame on. Whether it's improper use of the achievement system or not, the negative impacts are still there. Whether it's the devs, the publishers, the players or whoever you want to blame for it who is truly responsible... it all comes down to the system having negative impacts.
If you've done something worthy of an 'achievement', does it really matter whether or not you get a cute little icon to go with it? You know you've done it and why should it matter two tugs of a... well... who else knows about it? E-peen measurement is bad, hmkay? Besides, you counter yourself with the next bit about how 'a lot of games just puts the achievements there for beating the levels' and so on. In doing so making them practically worthless once more.
And I'm not even remotely upset that 'tweaking disables achievements'. I'm in fact a proponent of this, since that allows me to kill off the achievement system by tweaking something that doesn't really affect the game's difficulty. What I'm annoyed by is that games being practically forced to have achievements equally force a lot of devs to completely remove the option for tweaking. Games are getting consoles disabled and complete removal of cheat codes and so on because it's too costly to start adding features like "If console is used, disable achievements on this savegame" and so on, especially when you get to more complex games. This has happened a lot, sadly. Killing off something integral to PC gaming just because people hanker for worthless icons.
This also adds risk to everything by forcing people who need to tweak a game to run well on their systems to download trainers and config mods from third parties that can't truly be trusted. Take Dead Island as an example. Complete lack of tweaking options to the point where it's practically an unplayable game on a lot of systems. (Don't blame the hardware, I myself ran it on an Alienware m17x r3) To play the game I had to download a third party application to tweak the settings. None of it changed the difficulty or anything, but it was completely locked out by the devs. This happens a LOT in games to prevent achievements being cheatable.
I'm not saying achievements have absolutely nothing but negative impacts, but nor do they have any real positive impacts. Beyond e-peen measurement they provide nothing that the gamers don't aim for anyway once they try to add some challenge to themselves. On the other side, they have a lot of negative impacts. Multiplayer and singleplayer.