“The RZ would say that the gedolim in past generations would react the same as they did to the opportunity to populate and build Eretz Yisroel, which wasn’t possible in the past.”
1. What do you mean by “opportunity”? Weren’t the zionists the ones who created the opportunity? Why couldn’t that have been done previously? (It’s possible you are right and it couldn’t have been done – I am just wondering why.).
2. Maybe I’m wrong, but I didn’t think that the Mizrachi movement was started by Gedolim or that there were any Gedolim who considered themselves Mizrachi. But again, I could be wrong.
For them to talk about what the Gedolim in the past would have said is ridiculous; you have to listen to the Gedolim of your times. And that is what the Chareidim were doing. And that is what the Yidden in all the generations past had done, and that is why they are a continuation of the past.
3. Even if there were Gedolim at the time who aligned themselves with the Mizrachi movement, today, I’m fairly certain that there aren’t. In any case, the Chareidim are certainly following the majority of Gedolim and the biggest Gedolim, if not all of them. So they are doing what Am Yisrael did throughout history.
4. Furthermore, Mizrachi was a new movement. All the Chareidim did was to not follow it. Saying that is a new movement is like saying that not being Chassidish is a new movement. Maybe the Chassidim thought that the Gedolim in past times would have become Chassidish. But that doesn’t change the fact that Chassidus was a new movement and not following it is not a new movement.