In my commentary to Yevamot 3a (see https://rabbijohnnysolomon.com/yevamot-3/), I referenced Yevamot 39b, because it is here where Abba Shaul teaches that the only instance where Yibbum is not considered to be a transgression of a forbidden relationship is where Yibbum is performed לשם שמים (for the sake of heaven) – which is why Abba Shaul in our daf, and many later authorities, rule that Halitzah should be the preferred path over Yibbum in almost every case.
Specifically, in February 1950, the Chief Rabbinate of Israel declared that, ‘given that in our days it is clear that most levirate marriages are not done with the pure intent to fulfill a mitzvah, and for the sake of ways of peace and unity in the State of Israel, so that the Torah may not become like two Torahs, we hereby establish for all the inhabitants of the Land of Israel and for all immigrants who my make aliyah from this point forward, that it is completely forbidden to perform the mitzvah of levirate marriage. All are obligated to perform the act of halitzah. A levir is obligated to support his brother’s widow in accordance with the ruling of a rabbinical court until he performs halitzah and exempts her from the levirate marriage. Dispensation to permit levirate marriage against this prohibition can only be given under special circumstances and with the decision of the Expanded Council and the signature of the Chief Rabbis of Israel.’ (as quoted in a footnote in Responsa Heichal Yitzchak Even HaEzrer 1:5)
However, while this decision was made jointly by Ashkenazic Chief Rabbi Herzog and Sefardic Chief Rabbi Ben-Zion Uziel, some later Sefardic authorities – and most notably, Rav Ovadia Yosef – strongly opposed this decision given the fact that yibum had continued to be practiced in Sefardic communities as a preference over halitzah as per the Shulchan Aruch (Even HaEzer 165:1). As such, Rav Yosef ruled that yibum could, and should, continue to be practiced (see for example Responsa Yabia Omer Vol. 8 Even HaEzer 26).
There will be those who think that Rabbi Yosef was correct to stand up for, and protect, the customs of the community that he represented which he felt were being marginalized and, in this case, delegitimized. At the same time, there will be those who would agree with the reasoning of Abba Shaul that given the various moral and ethical challenges presented by yibum, and – as noted by Rav Herzog – given the way that the law of yibum may be perceived by some in the modern age, that we should follow the halachic view of prefering halitzah over yibum. Yet what is clear is what may have been more commonplace in practice in the past, is now less commonplace in the present, and this is likely due to the concerns and considerations first raised by Abba Shaul.