On one hand, Create Issue Meta Endpoint Deprecation should be pretty easy to pick up since there is a new endpoint matching your way of asking for the data by project and id:
- Get create field metadata for a project and issue type id: fetches a specific Issue Type for a specific Project via issueTypeId. This endpoint will have expanded fields by default and will support pagination on the Fields.
Since the fields are expanded by default, you should get what you want with less struggle against the Forge route macro. Hope that helps.