RSRH views the approach of the Rambam’s Moreh Nevuchim as fundamentally flawed in that its starting point was philosophical concepts that were learned from outside the Torah and the reasons behind the Mitzvos were then made to conform to those views. He felt this was the same approach that Moses Mendelssohn had which led to his students and the next generation abandoning and fighting Mitzva observance.
See much more on this in the 18th letter of The Nineteen Letters.
