Rails has several pain-points for more complex web applicatoins that frameworks like Hanami and Trailblazer attempt to address. By addressing theses issues your business logic is better isolated from the framework details/implementation, clearer responsibilities, easier reasoning about, cleaner code, creates opportunity for easy further abstraction when necessary, allows for simpler testing, etc.
Better file structure/autoloading that allows grouping of domain concerns under a single folder structure
Solutions: use custom autoload_paths/eager_load_paths in an initializer?
Solutions: Enforce this at the developer/code level - made feasible by using transaction, validation and form objects
Solutions: dry-transaction? active_interaction? custom "service objects"?
Solutions: draper, dry-view, custom
Solutions: (reform, dry-validation, custom)
Lots of json serializers to serialize rails models to json, but no standard for the reverse process.
Solutions: (dry-validation, custom)