I mean, as a flagship, it's specs are pretty decent, I think. The processor is a split Quad-Core architecture (nothing extravagant by any means with hexa-cores being fairly common). The RAM is substantial. No more 16GB option, and the added ability of microSD storage. A 5.5" display with 535ppi, not stunning, but not too underwhelming imo. Huge battery size, so theoretically pretty decent battery life. Ditching the 3.5mm for a USB-C is a fair move in my book. Camera looks pretty good. Aperture is a tad on the small tide, but everything sounds quality. The optional Moto Mods look like a bit of a gimmick, but extra battery life can't hurt, and the option to change the backplate designs on the fly is a bit neat.
Really the only thing I see that this phone doesn't have going for it as a flagship status device would be more processing cores, and dropping Moto ShatterShield and going back to Gorilla Glass. Maybe stereo speakers if I'm nitpicking.
Having bought the Moto X 2nd. Gen pretty soon after release (~3-4 months) I've never noticed anything groundbreaking about it either other than the semi-custom backplate designs.
I'm honestly not looking to argue or start a war of any sort

, but if you get the time, would you mind elaborating on what underwhelms you so much about the Z, I'm genuinely looking for some good insight.