I really haven't gotten a chance to play with Micronaut. I have an internal tool that needs to be rewritten for our Docker/K8S initiative and thought about a REST API using MN instead of Grails (it's currently written in Grails as just a standard web app with GSP, etc.). While it would be fun to learn MN, Grails actually is very efficient at cranking out those type of MVC applications and I'm not sure it would be worth the extra complexity of having to build out a React or Angular front end.