I suppose that depends on your RTO. With cloud providers, even on a bare VM, you can to some extent get away with having no IaC, since your data (and therefore config) is almost certainly on networked storage which is redundant by design. If an EC2 fails, or even if one of the drives in your EBS drive fails, it'll probably come back up as it was.
If it's your own hardware, if you don't have IaC of some kind – even something as crude as a shell script – then a failure may well mean you need to manually set everything up again.
Well, sure – I was trying to do a comparison in favor of cloud, because the fact that EBS Volumes can magically detach and attach is admittedly a neat trick. You can of course accomplish the same (to a certain scale) with distributed storage systems like Ceph, Longhorn, etc. but then you have to have multiple servers, and if you have multiple servers, you probably also have your application load balanced with failover.
If it's your own hardware, if you don't have IaC of some kind – even something as crude as a shell script – then a failure may well mean you need to manually set everything up again.