If it takes more than a month to migrate a 20-node K8s cluster, then that's a red flag. Too much tech debt or a strong vendor lock-in? Either deserves attention.
Doing the migration might take a few late evenings; deploying all our apps and Helm charts to a new cluster takes just a few commands. Learning what needs to be migrated, deciding on how the configuration should look on the destination end of it, and designing a detailed plan and checklist for the whole process is the big task. Adding the onboarding of someone who's never seen the inside of your company and you're talking about a longer, more disruptive process. Tech debt isn't a factor here.