AWS is probably the best actual CaaS vendor out there. They have a product offering expressly designed to help their customers get through this jungle:
https://docs.aws.amazon.com/artifact/latest/ug/what-is-aws-a...
You are still responsible for everything on top of what AWS provides (software/configuration/policy), but their compliance package handles a massive portion of what you would otherwise have to do if you were on-prem. Physical security, hardware management, disaster recovery, et. al., you get essentially "for free".