If you understand the difference between a slash, hack, slice, and cut, the pushdagger is a very good knife with some real utility functions.
They are not good for hacking, but they are competent slashers. Yeah, the technique is different, so what? You you try to use a hammer like a screw driver? They are different tools that require different techniques, but are equaly useful.
Push daggers are great slicers. Not the best maybe for precision work, but for opening boxes, slicing pizza, stuff like that, they are fine.
They can cut well, but it takes some getting used to. Again, not the best for delicate work, but they're fine for bigger stuff.
When it comes to fighting, you can't really find a better thruster. They shouldn't been seen as unskilled weapons either. Sure, you can use them like throwing a punch, but you can use a straight handled knife like a truncheon. Of course that places needless limitations on your technique. You can do things with the pushdagger you can't with your fist, and you should train to make use of that.
ComTech had a video on their combative use, I never saw it, but most of their stuff is good. The thing to remember is that they are only a one-trick-pony if that's what your mindset is. Were it not for legality questions, I'd pack one. Dammit, I need to get my concealed carry permit!