I'm in the middle of architecting a Grails 3 app based on the microservices project structure. Based on Jeff Scott Brown's video on how he separates the Web UI and the backend by using two Grails apps, isn't the Web UI app an overkill, compared to using an AngularJS based html?
Please do point out the benefit of using a Grails Web UI app if any.
I know it is one year later, but since I wondered the same here is my conclusion.
The presentation of Scott Brown misses the point of micro-services. They are not just small pieces of code that provide a RESTful interface, but they are defined as micro, by their footprint and the fact that they can live separate from each other. Try running a Grails instance for each small service. The cost will be huge as each machine requires more than 1GB ram.
To answer your question; monolithic frameworks as Grails are great toolkits, making it easy to handle and maintain more complex logic, as well as handle security and other common tasks which with (e.g.) Node you would need to install libraries of dubious quality or implement them yourself.
My take on the general aspect of micro - services or monolithic frameworks is that if you need simple data access and you are worried about scaling or you need a flexible way of distributing then use micro-service frameworks. If you have a complex business model or you need to use the tools in the framework use a monolithic framework. Finally, don't forget that no one is stopping you from using both simultaneously if needed be. It's a valid strategy.
I suggest watching Martin Fowler's "Microservices" talk.