«إِنْ هَذَا إِلَّا مَلَكٌ كَرِيمٌ»
This is nothing but a noble angel.
In here is negative and illā introduces the exception, giving the phrase a restrictive form. Calling a human being a noble angel expresses extraordinary admiration in context.
The restrictive syntax and hyperbolic figurative assessment can be analyzed together. Neither requires the conclusion that the person is literally an angel.