Bikepacking - a viable alternative to racks & panniers

Coincidentally to the recent conversation here around tailfin vs rack+bag, I've been back and forth with a friend about the same. I think I'm in the rack+bag camp, primarily because of cost. I have no doubt that the tailfin works well, but when I priced the tailfin and all the accessories that would replace rack/bag/panniers, I could buy a decent used bike for the total. That seems silly.

Using bits I already have on hand I could get the same result within a few grams, and not have to sell a bike to do it.

Advantages to the tailfin:
-mounting versatility for bikes without eyelets
-sleek design
-instagram points
-folds flat for travel with the bike

Advantages for rack+bags:
-many of us probably already have a good bit of the stuff needed
-significant cost difference
-retrogrouch points
-versatility in what bags and things it can carry

Example:
The blackburn EX-1 that I have on my Rove is claimed 535g though I suspect it's a bit more. I am however using nicer mounting struts and hardware from a tubus rack and suspect that it's lighter than with the stock flat steel hardware. The rack can carry panniers, rack top bag, drybag with straps, and even the child seat that my youngest rides in. I don't think I'd get very far trying to strap a 2yo to the tailfin.

I've done trips offroad with saddlebag/framebag/bar bag, and I've done similar trips with panniers and an ancient old man mountain that I've had since 09-ish. Both fine, and I prefer packing in panniers. Light panniers with secure attachment with straps are great on dirt roads, but I wouldn't use them on a purely trail trip. A bit too much "tail wagging the dog" for my liking. That's where soft bike packing bags win for me.