PBA:
I agree that circumstances, tactics and practical matters could change, such as, perhaps, voting in Israel’s elections, for example.
Meaning, if there is no inherent issur in doing a particular action, then that is something for whoever is the “shofet” “baYamim haHeim” to weigh and conclude if there is, in fact, any issur in doing so at that particular time and place, etc.
But there is no way to, for example, retroactively kasher [founding] the State which was and is a blatant violation of multiple issurim including a violation of oaths and (even the Zionists admit this and grapple with it in YU’s latest “To-Go” publication) pikuach nefesh (or, as the Brisker Rav held, the entire Torah).
The gedolim paskened as such having nothing to do with what Israel would or wouldn’t develop into and nothing can later make kosher what was a paskened unequivocal issur.
So what did you mean by “Nor do I accept the notion that because gedolim were opposed or supported something 50 years ago, that their opinion would not have changed if they had seen what the thing had developed into.”