I don't understand your reference to Yiddish here. The Zionists were opposed to the use of Yiddish.
There were different ways that Jewish nationalism developed, not all of them Zionist. There was the "diaspora nationaism" of Simon Dubnow, the Jewish Labor Bund, and so on. There was indeed a heavy emphasis on Yiddish among the non-Zionists, exactly because Yiddish was the language that many Jews, to understate the case, spoke. What was "invented" about it?
Personally, I am sympathetic to some of these outlooks, and am mildly involved in some of the remnants that still exist today. Of course, when you come right down to it, it's basically incoherent, because actually trying to define "Who is a Jew?" is impossible, in my view. But so what? Why should anybody care how others define themselves, or how they like to celebrate holidays, or whatever, as long as it doesn't interfere with others' lives?
Matters are different with Israel, of course, because there "Who is a Jew?" is an important question that cannot be ignored. The Avnery article is good, although I wonder how much of the initial compromise with the religious groups was because they needed to decide "who is a Jew", and so handed that over to the rabbis.