There was no “modern orthodox” leaders that created their movement the way l’havdil the baal shem tov started chasidus or rav yisroel salanter the musser movement. Instead, modern orthodoxy is just a bunch of people who like what the gentiles think and do, and to one extent or another, morph judaism to fit in, and then they spend their time putting major effort into figuring out what modern orthodox means. The root problem with Modern Orthodoxy, the issue from which stem all other issues, is that they incorporate secular, non-Jewish, values into their religious practice. What the secular world values, they believe is valuable. What the secular world thinks is normal, civilized, sophisticated, good, and proper, they do too, and they incorporate those values and attitudes, which are often corrupt and against the Torah, into their religious practice.
And so, because in the secular world, a “people” is bizarre when when youre talking about a people with no country and no common language – imagine the Italians without Italy or Italian – therefore, Zionism, which, to their standards “normalizes” the Jewish nation (that was actually the word the Zionists used) becomes almost a requirement of Modern Orthodoxy; because secular studies, college education, mixing of boys and girls and a general a collegiate, yuppy lifestyle, is considered “normal” in the secular world, it become part and parcel of the MO lifestyle.
And ironically, where college and mixing of the sexes is concerned, the MO community become tremendous meikilim way beyond what the halachah allows. In these areas, they will struggle to find heterim, whether they exist or not; on the other hand, regarding making aliyah, they will become fanatical machmirim, and despite the myriad leniencies and historical precedent of Jews willingly living outside of Eretz yisroel, they will often run around saying that you have to make aliyah, and not to do so is in violation of the Torah.
When secular values demand they be fanatical machmirim, they become fanatical machmirim; when secular values demand they become unreasonable mekilim, they become unreasonable mekilim.