Rav Aharon Kotler ZTV’L, in Mishnas Rabi Aharon (Vol. 3, Hesped on the Brisker Rav) states that the essence of Modern Orthodoxy is the same as the Reform and Conservative.
I guess this is a point where he and the Rebbe agree.
Here’s an excerpt from a 5717 letter of the Rebbe:
“This is also the case with regard to the person to whom you refer in your letter, who obviously does not belong at all in the Conservative movement, nor in the so-called “New” brand of Conservatism, which goes under the name of “Modern Orthodoxy.””