Understanding the words of the Ksav Sofer requires a specific historical context. He would never have needed to state what every child knows; that all the mitzvos of the Torah are obligatory, both bein adam lamakom and bein adam l’chaveiro.
The Ksav Sofer succeeded his father as Rav and Rosh Yeshiva in Pressburg. Hence, his fight against the Reform was foremost in his mind, as it was with his father. This vort on the pasuk relates to the movement to abandon bein adam lamakom and concentrate only on bein adam l’chaveiro. It was not a chiddush, rather it was a lumdishe rebuttal.