and try to order them during spring or fall because extreme heat and cold will kill them even with the good packaging.

I ordered 3 Bettas from Thailand and they were packed in double plastic bags with heat packs designed to travel with fish. Pretty ingenious. All 3 got here just fine and they are *lovely*.
Most sellers on Aquabid explain how they ship fish and also have feedback ratings so you can see how they’ve done in the past.

I agree it seems mean, but the thing is, they do all they can to reduce the stress for these fish.
Usually they use breathing bags (lets oxygen in and gas out) and something called bag buddies (it reduces the movement and conditions the fish.)

I’ve had success when I ordered guppies from a breeder on ebay.

They are in water and sealed air. The amount of air is enough to to keep them alive during the trip.