R Shlomo Aviner (at the very bottom of here) uses this Rambam to forbid vacation outside of Israel for those who live there.
The primary prohibition of leaving the Land applies only when one intends to establish his residence outside of Eretz Yisrael, but leaving temporarily is more lenient. Yet, he qualifies this leniency and writes that there must be some sort of concrete need for the person to leave.
Accordingly, it would be prohibited to leave Eretz Yisroel for a vacation if the trip does not serve a constructive purpose. It would be permitted if it serves a constructive purpose such as seeing the wonders and beautiful parts of Hashem’s creation, resting (when this cannot be easily achieved in Israel) and so on.
Writing more recently in OU Torah Tidbits (here, p. 68) R Shimshon HaKohen Nadel further comments on this Rambam
the Rambam's source is unclear. Upon further inspection, it would appear that the Talmud limits this prohibition to Kohanim. The Talmud (Shabbat 14b), teaches that Yosi ben Yo'ezer and Yosi ben Yochanan decreed impurity, on the 'Lands of the Nations', i.e. all the land outside of the Land of Israel. In his commentary to Ohalot (2:3), Rambam explains that the reason for this decree was that the gentiles were not careful to mark their graves. All of Chutz La'aretz therefore has a status of Tum'a d'Rabanan, rabbinic impurity, just like a Beit HaPras, a field of graves that was plowed under, which is suspected to contain human remains. A Kohen is rabbinically prohibited from leaving the Land of Israel and entering the Diaspora, as it is impure.
But the Talmud (Avoda Zara 13a) states that a Kohen can go to Chutz LaAretz for a court case, and pass through a Beit HaPras in order to fulfill a mitzva like marrying a woman or studying Torah. These conditions override the rabbinic prohibition.
But the Maharit (Kiddushin 31b) rules that the prohibition in leaving the Land of Israel is only if the intent is to settle permanently in the Diaspora. Based on this, many authorities are lenient regarding visits abroad (See Shevet Halevi 5:173 [quoted above]; Yechaveh Da'at 5:57; Tzitz Eliezer 11:94, 14:72; Magen Avraham 531:7; Tashbetz 3:288;).
אבל לשכון בחוצה לארץ אסור The very Rambam you quote is clear the issue is not short visits, he states living outside of Israel is the forbidden.