When you say "some assembly required" I take it you mean a bouquet where you add the plant food to the water, put it in the vase (your own or one with the flowers) then open the plastic wrap round the flowers and arrange them? Because that's what I would expect from a delivery web site, I think it's the only way to transport flowers so that they have a decent shelf life, so to speak. Once they're put in water they're much harder to transport. Were you expecting a bouquet already arranged, delivered in a water filled vase? I don't think I've ever had flowers delivered like that. So I don't think what you got was unreasonable, or a rip off. I would be concerned about them being dumped on your doorsteps though, especially in the snow.
That's what I was wondering.
I got some flowers from my BFF a couple of weeks ago (she always sends me flowers on my birthday

). They came in a box, wrapped in cellophane, with a moisture pack and a little packet of plant food. That's how all the flowers I've ever received 'delivery' have come.
I also agree that my issue in your case, OP, would be with the delivery people (whether that was the florist, or some other company). Presumably it was obvious that there were flowers in the package, so dumping it on a doorstep, particularly in snowy conditions, would be unacceptable to me. Also, if it was "flung haphazardly", as you said, was there any damage to the vase? They're fragile things, so if it was unharmed, surely that shows that it was well-packaged by the company.
To be honest, Knitterly (and I really don't mean this to sound harsh), but in future, I think you should encourage your DH to buy flowers at a local florist and bring them home himself / get someone to bring them to you. In my experience, what you got is how delivery flowers work.