The problem is that part does not cancel the other part. And that is where the troubles begin. Some people notice that in fact there are plenty of things that the Torah requires of us that are strictly between man and God. E.g. the whole Temple service which takes up a good part of the book of Leviticus, Shabat, etc.
The trouble is that when people start to notice these other parts of Torah, the between man and his fellow man parts tend to disappear.
I don't think there is any good solution to this problem because men are programmed to be able to concentrate of only a very small set of principles in their daily lives. 613 principles are just too much.
So people try to distill the essence of Torah and package it. And they don't usually get it right at all.
The approach that was tried by Israel Salanter seem was intended to address this problem. That is he looked at the books from the Middle Ages that addressed both of these aspects of Torah and he saw that they were in fact very effective in helping a very great tzadik, Shmuel from Salant, to reach the kind of balance that the Torah intends.
So the Musar approach I think I would have to agree with.--with one addition. That is books of השקפה also from the Middle Ages. That is the Rambam, and the other thinkers that were interested in defining the basic world view of Torah. But if there is much today that reflects this I doubt. To some degree the Religious Zionists have this approach but only approximately. While they do try to find this balanced approach still, I am not sure if they have reached it. The Mir Yeshiva and the normal straight Lithuanian yeshivas where I learned also seemed to be close to it, but not exactly. But these last two approaches seem to be about the closest I can imagine to striking this balance.
[The Religious Zionists are right that the Torah is very interested in getting Jews to Israel. That is the reason the Red Sea was split and it also is the subject of prophecies of all the prophets. The normal Litvak yeshivas however are lot better when it comes to learning Torah. But the fact that one group emphasizes one good trait and the other emphasizes another good trait is no reason to complain about either group.