As far back as I remember, as a very young child, “Eretz Yisrael” was a part of the Judaism I grew up with. Before I ever heard of Zionism, Politics, or Refugees, there was a place called Eretz Yisrael, part of our lexicon both at home and in school. It was definitely not to “sound” frum!
Avrohom Avinu was promised that Eretz Yisrael would belong to his decendants. Getting us into Eretz Yisrael was was one of the significant things Hashem did with us after He took us out of Mitzrayim, sung with gusto in Dayeinu. That was the place that Moshe Rabeinu begged to enter, and about which the meraglim spoke negatively, much to our detriment for thousands of years since. Eretz Yisroel is/was the land referred to in Shema; in the parsha of “Vehaya im Shamoa”, which we were warned we would lose if we turn away from Hashem. You get the idea. There was never any reason for me to start calling it Israel!
As an adult, I do sometimes use the term “Israel”; mostly in political discussion, or when checking flight arrivals and departures.
At times, it does somehow sound less complicated to just say “Israel” when referring to my destination for a yomtov, or a place to learn Torah. However, when I do that, it really feels empty; like something is missing. The depth of its meaning to me, and the kedusha that is woven into its fabric, somehow feels incomplete when I refer to it as Israel. Israel is just another location, albeit where many of my relatives live. Eretz Yisrael is the holy land, given to us Jews, by Hashem, and it is that holiness that is the basic reason that we go there, despite terrorism, and despite the fact that there are many other beautiful places on Earth to visit.
It’s not a frumkeit thing. It’s an identity thing. “Israel” is just too shallow a description for a land with which I have a relationship! Eretz Yisrael describes the only place I know which transcends the description of a location.