Could you explain the meaning of the sentence in bold? Does it use an idiom?
Sesame Street is...with lapses, the most intelligent and important program in television. That is not anything much yet. Renata Adler, The New Yorker, 1972
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Basically, Adler is denigrating the quality of television shows in general. She's implying that the only reason Sesame Street is the best is because all the other shows are lousy. It's like saying "I'm the richest person in the room" because I have a dollar and nobody else has more than a quarter; it is technically true that I am the richest person, but my so-called riches are "not anything much yet", that is, they are nothing in comparison to what is normally considered rich.
It is equivalent to saying
'This is nothing important for now.'
The phrase 'not anything much' means nothing important/impressive (source).