With another European airline I recently waited exactly one day less than the three weeks required for them to deliver a child seat. That’s almost three weeks of not having one to safely transport my child, no support or compensation. Since I was returning to my country of residence the credit card company also didn’t refund.
Why not just buy a new one and charge the airline for it?
For a baby car seat, probably not worth it. For other things it might be but the receipt is missing etc.
At the end it's a damage you have to face for them not doing their job right.
That seems pretty unlikely; the receipts now go to your email where you'd have to delete them intentionally.
In my case, I think they deliberately bumped my bag for paying cargo, because they saw my billing address was near the destination airport and assumed I would be fine "at home". They didn't know I was going to a wedding, and that said wedding was several hours drive away, so delivering my bag a day late to the destination airport wouldn't end the problem. They still paid out though.
You already need to insure higher values anyway if you want to be entitled to a reimbursement, so this would set a nice minimum that encourages customer friendly behavior.