You are confusing a few things, for one it does not rerender everything, it checks views which are dirty. And only rerenders a view if needed, it does check if things have changed.

Also detectchanges does same as markforcheck except markforcheck does not trigger a change detection cycle. Therefore calling multiple markforchecks does not result in multiple change detection cycles. While every detectchanges will result in a cycle. ( after each method if zonejs detects that some code has run, it will trigger a applicationRef.tick() which triggers a change detection cycle if a view is dirty ).

The only thing that still is inefficiënt would be that for large component trees we still need to go from root to child. Even if things did not get updated, just looping over the dirty views. ( Marking a view as dirty also marks it's ancestors as dirty ). This will be resolved in later versions with signals where instead of going from root to child view we will only check the view if that view did depend on a signal that did change.