I mentioned that Schonberg felt the way he did since the 1960's to show how long he felt this way about pianists from the first half of the 20th century vs. ones from the second half. To say that the last 50 years(1960's-present)have not produced many very great pianists is an extreme view I think. I think it would have far more reasonable for Schonberg to simply state his personal preference for the playing style of the earlier pianists rather than claim they were inherently superior.
Schonberg does talk about different qualities of pianists of his time and he does praise some of the very names you mention (Argerich) for technique and temperament. Since you do not trust this particular Schonberg too much, why not listen to another fellow with the same name? Here's a nice quote:
“Today’s manner of performing classical music of the so-called ‘romantic’ type, suppressing all
emotional qualities and all unnotated changes of tempo and expression, derives from the style of playing
primitive dance music. This style came to Europe by way of America, where no old culture regulated
presentation, but where a certain frigidity of feeling reduced all musical expression. Thus almost
everywhere in Europe music is played in a stiff, inflexible metre - not in a tempo, i.e. according to a
yardstick of freely measured quantities. Astonishingly enough, almost all European conductors and
instrumentalists bowed to this dictate without resistance. All were suddenly afraid to be called romantic,
ashamed of being called sentimental...Why is music written at all? Is it not a romantic feeling which
makes you listen to it? Why do you play the piano when you could show the same skill on a typewriter?
(...) It must be admitted that in the period around 1900 many artists overdid themselves in exhibiting the
power of the emotion they were capable of feeling. (...) Nothing can be more wrong than both of these
Who is talking? Arnold Schoenberg, in 1948, about the general shifts in performance traditions.
Somewhere in this interview, William Kapell shares his thoughts on the topic, mentioning how there was a reaction against the perhaps overly "subjective" and free aproach in the early 20th century which was replaced by more "objective" playing. The interviewer here is of the opinion that William Kapell's playing combined both.http://www.youtube.com/watch?v=NKzYpgS7gh8
Besides, you have to realize that Harold C. Schonberg wrote this article reflecting upon "young talent" he's been hearing taking part in some of the worlds biggest piano competitions. He's pointing out a very GENERAL trend among young players (and slightly older and more experienced ones) of the time as opposed to general trends of the past. The point he is clearly making is also that many of these past masters that he respects had very clear links to the composers of the romantic era, which clearly gives them a certain credibility. If Liszt taught someone, hailed this person as a genious at the piano, and this person recorded and wrote about Liszt's teachings - ought we not to read and listen?