The basic approach of Reb Israel Salanter is much more significant than most people realize. It contains the seed of the new future. The modern world as is seen clearly is in the decay of post modernism. There is no unifying factor as faith was during the Middle Ages. But the Middle Ages still provides the seeds of the future. The books of Ethics written then.
[Civilization needs certain unifying factors. Though faith was certainly that factor during the Middle Ages, that faith needs some kind of synthesis with later developments. The Middle Ages got a lot right--much more than we admit today. But still there were areas that were naive.]
One important insight of the Middle Ages was the synthesis of Faith and Reason. They knew very well that religious fanaticism is poison. But they also knew the need for faith and morality based on the Torah. [The Middle Ages had a great idea what to do with religious fanatics-- lock them up in some institution where they can do their thing without bothering anyone else.]
[ In the Middle Ages synthesis of Faith and Reason meant (more or less) Torah with Neo Platonic thought. The tilt towards Aristotle happened almost towards the end of the Middle Ages. Both Maimonides and Saadia Gaon were Neo Platonic.]
[I was never that much into the mind set that looked down on the Middle Ages. But going to yeshiva in NY was even for me a eye opener. The son of Rav Freifeld [Moti Freifeld] told me "Rishonim can not be wrong. Achronim can be wrong."] ["Rishonim" means mediaeval authorities. Achronim means authorities from the Beit Yoseph and after-including the Beit Yoseph (Rav Joseph Karo)]
Besides that it always was (and still is) the basic emphasis of all authentic Litvak yeshivas to emphasize rishonim.
[From where this idea of the superiority of the modern age over the Middle Ages is not clear to me.--To some degree it seems to be a result of realizing the advances of the Renaissance and later on advances in the natural sciences. But the Renaissance is not the same things as the Enlightenment which seems to have gotten almost everything wrong. "What is Enlightenment?" is Kant's famous question. The simple answer is, "Everything that tries to undermine faith. It was a movement directly specifically to bringing down Throne and Altar."
But within the context realizing the importance of rishonim [medieval authorities], I find some acharonim [later writers] to be of great benefit. Mainly I am thinking of Rav Shach and the Maharsha.
[But there are also some more achronim I found helpful, e.g. the Pnei Yehoshua, Reb Chaim Soloveitchik. ]
