I agree that some clients with legacy processes want consulting support on implementing agile, Github and source control, setting up CI/CD etc. as you say. But for most clients this has been done already and they are more interested now in how to integrate the new AWS and Azure services into their product development so as to cut their dev time and costs. Development or build will still dominate their total costs and the prospect of leveraging best in class software as a service from the cloud providers is the real prize.
The choice of firm in the end comes down to the large branded consulting firms or the focussed devops boutiques. The large brands win on brand and often on industry experience but usually don't offer staff who want just to do devops and have so focussed their professional life on your problem.