"existential importance" is correct and usable in written English.
You can use it to refer to the importance of something in terms of its existence, such as the importance of living a meaningful life. For example, "Finding meaningful work has an existential importance that cannot be overstated."
Even those scholars -- in the main Ashkenazi Jews -- whose research has helped us to better understand Sephardic history have presented their work in a manner that does not consistently speak to the existential importance of this history and how it could act as an important bridge linking Sephardic Jews to the Arab-Muslim world.
Low birth rate and the negative natural increase is a matter of existential importance for Estonia.
For all the airline industry's running battles with authority, it has had a good run on an issue of existential importance to carriers: consolidation.
Virtual reality is about to hit the mass market, and it's not exaggeration to say that the next six months are of existential importance for the field.
The campaign seems to resonate with a certain existential importance for France, which once controlled a vast empire stretching around the globe.
The headlines had suggested he would be in his office at a desk or podium to share news of existential importance.
In contrast to Aristotle, Brentano emphasizes the importance of existential judgements with only one term, and claims that predicative judgements are a special case of existential ones.
The moral importance of existential risks cannot be understated: a cataclysm wiping out humankind would result in innumerable lives lost, both present and future, rendering current anti-hunger campaigns and infectious disease prevention programs practically futile in comparison.
At the very least, science-educated individuals—such as the undergraduate psychology students who constitute most psychology research samples may find themselves unable to reject ET as a way of assuaging existential anxiety, given the importance of ET to their psychology-student worldview.
Cancer 89 (8): 1854 1865 Cohen SR, Mount BM, Bruera E, Provost M, Rowe J, Tong K (1997) Validity of the McGill Quality of Life Questionnaire in the palliative care setting: a multi-centre Canadian study demonstrating the importance of the existential domain.
The importance of spirituality and existential concerns in health care settings has been firmly established within the biopsychosociospiritual model [ 1], and is now increasingly recognized beyond its initially limited applications with terminally ill and older patients [ 2].
