I don't mean their personal lives or any of that. What I mean...
My opinion is that... as pianists they are not very interesting. They are all praised for their talent &c (with good reason, they are all amazing pianists), but their interpretations are nothing extraordinary or remarkable (besides Horowitz's Op. 101 maybe, but)... Which is why I remarked that "they're posterity recordings". In the words of Gould (certainly the most interesting pianist, as he had more to say about music and his work than any other musician), "all the basic statements have been made for posterity". A personal example, I never listen to many of the Beethoven sonatas anymore because I've heard the same Moonlight sonata, Op. 90, etc. interpretations too many times already, and they no longer interest me. Of course the phrasing is nice and the touch of the pianissimo is just right, and whatever else... But how many times can one listen to such a piece and be interested simply in the sound the pianist produces?
None of the pianists I mentioned had anything very remarkable to say about music either.
Hmm - it seems you have never seen Schnabel's Beethoven editions, or Arrau's interviews on music, or listened to a single Horowitz record besides op.101.

Based on your comments, I would say the problem lies with you, not the pianists. Who says you have to listen to a piece to hear the touch and the pianissimo?
When I listen to Kempff, for instance, I am totally engaged by the narrative continuity. He is able to make the Brahms late pieces come alive in a way I have heard almost no other pianist do, with the exception perhaps of Radu Lupu. It is not even about his touch or his sound, it's about the whole experience. His performances seem to suggest stories, running deep with characters and feelings and atmospheres, that go beyond any kind of physical approach.
The same with Horowitz. His playing is characterized by an impetuous electricity. You never know what to expect, but it always communicates so strongly this huge variety of images, like fire lighting up a horizon, or sparkling stars, or evil horned demons. I don't even think, "what kind of touch is he using on the left hand vs the right hand?" I see pictures when I hear him play.
Schnabel of course is able to convey the structure of music in a practically visual way. I can follow the pieces when he performs, as if they are going past me in a panorama. There are few pianists that play in that way; I would say another is Richter. Although Schnabel and Richter sound nothing alike, I believe they share this quality, of making the inner world of music visible. Not only that, but Schnabel was a cultural historian, which you can hear from his recordings and see from his notes on the Beethoven sonatas. He understood above all what was to be taken literally, and what was a keyboard effect composed into the music by Beethoven. Today, almost everything is taken literally.
For instance, compare Schnabels recording of op.10 no.1 in c minor with any modern pianist. You cannot have heard his performance, and said that he has nothing to say about music like this. His perception is totally different, on a fundamental level, from the mindless literalism that pervades piano-playing today. His kind of interpretation wouldn't get past any competition's recording round, and thank god; it just reveals how ridiculous they are.
Sorry you have such a dry opinion of these great artists!
Walter Ramsey