Agreed, it took me too many years to fully appreciate it for the masterpiece that it is. Quintessentially English, is how I hear ot now, steeped in a tradition of English romanticism (although I may be guilty of overthinking it 😀).
And yes, Norma's voice is very special. I remember hearing her live for the first time at one of Kenny Wheeler's birthday concerts (the one released by ECM) and being completely knocked out.