We weren't winning a war of attrition, and the rules of engagement were insuring there wasn't strategic winning either ... that happens when you try to close the wrong end of a pipeline, fight the wrong kind of war, and allow the enemy sanctuary.
Just talking about Tet and nothing more. That was definitely a loss for the other side, but the press made it out to be a US loss. A lie is a lie, no matter how you spin it. LBJ and McNamara lied to the country and to themselves about how things were going because they were cooking the books to make it look better than it was - fooling themselves in the process; so, yes, the press caught on and probably only because Tet got their attention by happening in places like Saigon right in front of them.
Whether the war was winnable can be debated forever, but almost certainly not by the Johnson/McNamara rules. The other part is the one about fighting an Asian war; we as a country lose interest when the bodies start coming home and then become antiwar; Asians are in it for the long haul, and we can't/won't match their patience. You either fight to win ... no holds barred, or don't go. Since then we've repeated the same errors ... just in new places. Technology probably will never defeat a low tech enemy at home in his own backyard and terrain to his liking (our own Revolution is a great example), but it sure is expensive. Makes you wonder how much wall just one day in Afghanistan or Syria would build.