You come up with "worse than useless" when the regulations make an inherently more dangerous structure have outcomes that are almost identical to the wider population?
Seriously, think that through. Prior to regulations high rise fires killed LOADS of people. There are lists of hotel fires that killed more than 10 people because these are deemed to be historically significant and yet there is only 1 in the last 30 years! And it was a deliberate arson for which the perp is serving multiple life sentences.
I'm not arguing that high rises are as safe fire wise as a standard suburban home, they aren't. But regulation of high rises has resulting in there being only nominal difference in their safety. If that isn't an example of regulation doing what it was meant to I don't know what is.
And I didn't bother looking for airbnb specific fires. Because there is no reason to. Given airbnb doesn't require any additional regulation then best case scenario is that it will have a fire rate the same as the wider building population. You can argue factors each way for higher or lower risk. But the sample size is too small and their duration of operation is too small to have a meaningful comparison.