Dear Always,
Assimilation was almost nil in the Arab lands, middle ages Ashkenaz, Czarist Russia, and other places for the same reason. There was nothing to gain. Not marriage, income, status, or meaning of life.
The Zionists were split in three groups. One was dedicated to the land – namely agriculture. They would have to meet like minded Arabs. Not likely. Two: were just looking for a better life. He they were not very opposed to assimilation they would have went to America. Three: were deeply attached to Jewish ideas. That would have needed to come upon an official platform as to why intermarriage is beneficial to Jews. As was widely done in industrialized Europe.
When I think about it, touched by modernity is relative. The people who were not, would have thought themselves as modern as they needed to be.