As early as 2008, Corey Ladas, who authored the book, Scrumban, made the observation that many Agile teams adopting Kanban dropped retrospectives. The function of the retrospective mostly moved to what I called the “After Meeting” which mimics spontaneous quality circles in industrial engineering. Such meetings are truly at the heart of a Kaizen (continuous improvement) culture. So there is no need for a formal retrospective on a regular cadence, its function happens spontaneously and on-demand. However, Kanban does include several other feedback mechanisms that are recommended on a regular cadence. The Service Delivery Review is the closest thing to an Agile retrospective but tends to be quantitative in nature. The Operations Review is a product or business unit wide roll up of the SDRs. This is not necessary in smaller organizations with only a single workflow or Kanban board. There is also the Risk Review which is primarily focused on the practice of clustering blocker tickets harvested from the Kanban board for the purpose of root cause analysis and prioritization of improvements that seek to mitigate or reduce risk or provide contingency planning against occurrence of such risks.

So while I wouldn’t be worried that you’ve dropped Agile retrospectives, as this isn’t a new behavior, and it is well documented that it has happened in the past for the right reasons and been a successful decision, I do believe there is value for an organization of your scale to consider value in studying service delivery reviews and risk reviews and perhaps adopting them with a monthly or six weekly cadence.