You’re right that that psak of the tzitz eliezer, who’s quoted a lot by the aforementioned nonchalant “Orthodox jews”, was extremely controversial. Maran Rav Moshe feinstein was in a totally different leafue than him, and not only did he say it is murder and prohibited in all cases, save for when the mother’s life is in jeopardy, but he denied the veracity of opinions to the contrary, saying that Hashem should forgive the achronim who wrote that it’s mutar in kach vekach circumstance.
This may not be easily palatable, but as someone who learns dibros moshe, I believe rav moshe was on the level of the early achronim. Besides rav akiva eiger, I’ve never seen anything like rav moshe, in depth, breadth, lomdus, rigor, comprehensiveness, everything. If rav moshe dismisses something as crucial as this, it is not to be taken lightly.
In any other area in halacha, would we say something is a “machlokes rav moshe and the tzitz eliezer”? They’re not in the same universe, as big of a talmid chacham as the tzitz eliezer was – he was, in fact, a big posek and wayyyy bigger than me and anyone else here, but nobody who knew both figures would compare them. The only people i would compare rav moshe with in his time were the chazon ish, brisker rov, tchebiner, satmar rov, and not many others.