The age of immutable inf. did not completely free us from occasional hotfixing production issues, because immutable deployment takes time, and if it's downtime you're accountable (as sysadmin/devops/whatever).
I also had a difficult time to explain that a prod deploy of 30min (image creation, deploy with blue green) is normal for this kind of inf... Did you face the same thing?
At the end of the day, if you're on continuous deployment, a commit should be rebuilding only what it touches. We have 4 min long deployments + 1.5 min tests and I definitely don't think we're optimizing aggressively.
Many places still keep producing very stateful software (sometimes even very much by choice) that is better off managed through Puppet / Chef rather than an immutable containerized approach. If your software needs to take an hour and a half to shutdown, for example, you have to get a bit creative with your deployment strategies.