I think the point here is that Rails is a very productive platform for building CRUD workflows - much more so than, for example, Go (perhaps less so for Phoenix

I think the point here is that Rails is a very productive platform for building CRUD workflows - much more so than, for example, Go (perhaps less so for Phoenix/Elixir). So you can build the vanilla CRUD screens in Rails in minimum time (and therefore minimum cost), where performance is not going to make much of a difference either way, then use Go microservices for those parts of your platform where performance is essential. So use each tool where it is best suited for the job - Rails for productivity and Go for performance.