It sounds like you think kubernetes et al. are a suitable replacement for ansible et al. , however k8s are not able to provision settings on a Web Application Firewall from F5 and the iLO links on your HP blade server farm. Et Al. Your statement works if you are letting AWS/MS/Google do all that for you and all you are responsible for are package dependencies and joining the right VLANs. Not everyone is so lucky and actual Configuration Management tools like Ansible+, while not perfect, make Domain Specific (i.e. real world Multi-Vendor) large environments run on time for most of the time.
And of course you’re right, the use cases don’t totally overlap. However there is a big chunk of the core functionality which is absolutely competing ways to solve the same set of problems.
