Yup--really bad idea. Ensured WWII...
...but that specific form of WWII, including the Holocaust, was less clearly predictable. Still...
...plenty of Jews left Europe before WWI, even (including my wife's grandparents) because it was already problematic there. Anti-Semitism has long roots and the Jews would have wanted, and benefited from, their own country even without WWII.
I was not really talking about Europe.
In pretty much all countries along the mediterranean coast and the middle east were enclaves of Jewish people.
But a lot of people left for the new world before WWI...so that is neither here nor there either.