You can roll your own anything with enough time and manpower. Whether it makes sense to do so depends on your circumstances.
For the last several years, due to static load we've been fine with 2 instances per service. Now that we want autoscale (even though all the real load is really just the DB), it seems we could get ourselves onto AWS autoscale in ~1 month, though it would require some coding.
Spending 3 devops on 1 year doing something is a red-flag to me. If your changes save devs 1 hour per deploy, it'll pay off 6,000 deploys from now.
I think it's great you guys have 2.5 dedicated people operating 6 services across 12 prod instances, with that kind of ratio our team would be 15 people!
When you make a change manually, there's a chance that you forget something, have a typo, etc. Those problems disappear when those same things are automated.
I've used Puppet, Chef, and Ansible in production over the last decade. For me, Ansible replaced Puppet and Chef five or six years ago. For the last two years the only thing I have used Ansible for is to manage desktops and Android boxes AT HOME. Configuration Management systems like Ansible are fun and cool, but have been mostly obsoleted by the combo of Terraform and K8s. If you're on AWS, Kops can replace a lot of what Terraform does.
Kubernetes makes running services easier and more reliable. I've spent more time learning Istio that K8s itself. The learning curve of K8s is minimal compared to Drupal.