But let me explain it, a seed in your comparison would be your rental contract, or your house document (authentication), Your monthly rental or purchase price would be your accounting. And authorization would be the key to your house.
The latter IOTA forgot to implement.
Clear now?
Anyone implicity trusting a unknown site to create a random seed is trusting the access to their funds to a stranger--either change the key (random char) or don't bother.
My analogy is apt as the seed is what you need to get in the house/safe--a piece of paper won't give you this acces or prevent a theft from someone with a key.
Again, where did the devs promise more than a bare bones wallet? Nice you have ignored this detail. Dom said he didn't want the Foundation building wallets--that includes idiot-proofing them.
You did a stupid thing, own it.