Absolutely the right security trade-off for Signal users. Anything else would devalue the entire product.

Whatsapp chose a different approach (which is reasonable for their user base) but that means that there is an escrow key. Regardless of your choices, messages that you sent may end up "end to end encrypted" but in reality stored in the cloud with a key escrowed to Meta...

The backup feature seems to be opt-in, i.e. the requirement to write the key down won't be too surprising.