I think the author of this article is quite right. When life is good in the Exile, a lot of Diaspora Jews want to stay in their host countries, especially if they have good jobs and strong ties there (friends, relatives, etc.). The more they become assimilated, the less they feel the desire, let alone the duty, to make aliyah. Also, one must keep in mind that Diaspora Jews develop a sense of attachment and loyalty to the country where they were born and where they live. A lot of them are ardent patriots in their country of residence. The more this attachment and this loyalty grow, the more they view their Jewish identity "merely" as a religious one or a cultural one (as a common history and a set of traditions). They do not view themselves as forming a distinct people. They do not consider themselves as American Jews but as Americans of Jewish faith. Those who have no faith (and there are many) consider themselves as Americans of Jewish origin. Those who are self-hating will even try to hide their Jewish "origin", which they regard as a meaningless "ethnical" or "folk" background. Actually, assimilated Jews strongly resent the notion that Jews form a distinct people as being "antisemitic" because they say it will be used by Jew-haters to claim that they are not loyal citizens and that they represent a fifth column.
That is how Torah-Judaism gets destroyed in America or in Western Europe : painlessly (Jews are "happy" there, as free and equal citizens in prosperous countries !) but very effectively. And we see "Reform Judaism" or "Progressive Judaism" flourish, as if you could remain Jewish while discarding the Torah !
The very powerful forces of assimilation in the West become hindered when antisemitism resurfaces. This is when Jews realize that, no matter how hard they try to integrate and assimilate, they will always remain Jews. In Europe, it led to terrible tragedies in the last century because European Jews had nowhere to go. But now that the state of Israel has been restored, Jews would probably make aliyah in large numbers if Jew-hatred surged.