There is a place for all solutions: 1- panniers for people who have to carry a ton of stuff,
2- trunk bags floating on beam rack or hard rack for medium volume of items, 3- cheap schoolkid backpack for those interested in cheap and non cycle bags, and 4- cycling backpacks with weight carried on hips and sternum strap to keep it from shifting.

For those unfamiliar, a good cycling backpak will keep the bag off the back and will have good air flow.

For me panniers have too much room and would really slow me down. The trunk bag worked well for transporting enought stuff to work to change at work. The beam pin broke and the rack won't work on an aero seatpost, so I have switched to backpack. I thought I would hate it for: a- too hot and sweaty, b- too many straps flopping around, c- all the weight on my shoulders, d-block vision and e- add more resistance and slow me down. It turns out I got a good pack and none a one of those assumed issues has bounced up. Only issue I have is I'm only using 1/4 of pack and so tend to put too much in it.