As a code developer, there is no reason to not keep coding. You don't have to deal with infra or packaging/deployment. It sounds like bad management on your company's part. In the few large companies I've worked at, software architects, programmers and DevOps were responsible for the different parts of what you mentioned. The architect designs and directs the "engineers" (software/DevOps). For example, "Java guys, please read all config from env vars", as part of good microservice design. Naturally, the service implementation itself should be part of a larger whole; most likely multiple small microservices. And you, the coder, just follow the design. DevOps take care of infra, ci and cd according to the same design. Overlapping domains are discussed and brainstormed.

Having said that, you are wrong in thinking you can learn something that'll last more than 5 years. It's possible but the field isn't about doing the same thing for a long period of time. The job description is better put as "quick learning capability". Which you said yourself; you need to adapt as time goes on. That doesn't necessarily mean AWS. It means Java WebFlux, in your case. AWS and k8s are, each, huge huge topics. They can each employ a team. You shouldn't dive deep into it unless you want to change career paths. AWS to become a cloud architect or k8s to become whatever-cool-name-that-hat-has. You can't be top gun Java dev and cloud architect. It's too much. Select few gurus could exist that excelt in both. But it's simply too much information to keep up with and not a realistic job description/requirement.

Bottom line is you need to continue to adapt in your field of choice (Java or AWS or k8s) and turn your critical eye to your own company. Something there sounds off. The DevOps guy should be the one to tell you lambdas can be written in Java. And the vprnd should be the one to choose Java, seeing as most of the company already knows Java. The architect can give you guidelines how to design your implementation to be compatible to cloud architecture. And you can just learn a few basics about AWS lambdas to be able to debug.

Anyway, sounds like a midlife crisis. Hang in there. I got myself a sports car.