Please calm down.
You can still assign roles in categories and use category enrolment plugin instead of cohorts. This enrol plugin is disabled by default. The new enrol subsystem is very flexible, if you really want you may tweak the category enrol plugin to make it work exactly like before (that is make it automatically create new instance in each course).
Cohorts are more flexible than the category enrolments especially when integrated with external systems.
Enrolments in 1.9.x were hardcoded to work one way only, now you can replace all plugins (except manual) and you can make it do anything you want. I had just a few weeks to write very basic plugins that work in a similar way like before.
If you do not like how enrolments work please please write new and better enrol plugins or improve current plugins.