I think the Z flip will certainly appeal to those people old enough to have some nostalgia about their old flip phones. I never personally owned a Razr, but did have one of the really old Motorola “flip” phones, but even back then when I wasn’t opening the phone hundreds of times a day, it was the hinge that ultimately failed and killed it for me.
The cell phone I really loved back in the day, was a super thin Sanyo that was billed as America’s thinnest. It was not only thin, but narrow too, so really easy to hold and stuff in pockets (except for the angled antenna). So of course I appreciate the push toward thin devices.
As others have noted, I’m not sure I’m in the camp of needing or appreciating a device that folds in half - especially if the drawbacks to make that possible are greater than the space saving benefit. It will be interesting to see what real world battery life is like with it. And how the screen and hinge mechanism hold up to pocket and bag detritus.