HaLeiVi: I am responding to the version of that Shittah that I saw (I think it was brought down in the Nitei Gavriel).
The Matzeiva is a bad example (and possibly Apikorsus if you take the analogy too far). HKBH told us at Mattan Torah that it was now an improper way to serve Him because the Goyim used it for A”Z Kodem Mattan Torah. To say that a Mitzvah can be changed like that Achar Mattan Torah might be Apikorsus.