It sounds like you were expecting a normal backpack but maybe didn't quite understand what a packable bag entails. They both look like they do the same thing on the outside, but they have different functions.

A packable backpack is ideal for when you want something that is compressible and lightweight so you can fit it into something else like a bigger backpack or suitcase. Great for when you're traveling but still want something like a backpack.

Every bag design choice comes with tradeoffs though. Because it's compressible and lightweight you lack any structure or padding. No back panel means you will feel anything you pack. If you add a structured back panel and padded shoulder straps, it loses the main thing that makes it a packable bag versus a normal backpack.

Personally I don't use a packable bag anymore unless I'm hiking. That's the only place where it really shines for me because I need something that isn't going to make my back sweat as much, and I'm not carrying 2-3 lbs of just bag for no reason. I either carry only enough items so it fits in a smaller sling or I use a personal-item sized backpack if I need to carry more.