We have observed that the adhoc subprocess give a hook to choose a task in it and to trigger at runtime. Can this replace most of the usecases of case model. I am concentrating on the overall functionality and not on constructs.
Like a sentry can be replaced with a flow condition. A ad-hock subprocess giving the flexibility to choose an activity to execute at runtime
For simple use cases: probably. But with CMMN you can model way more complex use cases that are complex and cumbersome to model in BPMN (if not impossible for some).