I don't know how historians will look at XX century.
Musical history would certainly have been the same if Dohnanyi had not written a note. But my life would have been the poorer too. I have always enjoyed his Nursery Song Variations (like many other people!) but my latest discovery is his Sextet for piano, string trio, clarinet and horn (thank you, Naxos).
You may know, trained-pianist, that in his lifetime Dohnanyi was considered by many to be the finest pianist since Liszt. What a pity that he left so few recordings.