The Christians I know are the PITA ones that are against everything
At the time Allhallowtide was formalized, believed to be by Pope Gregory III (731-741), all Christians were Catholics, excepting the Assyrians and Oriental Orthodox, who respectively broke from the Catholic church after the Councils of Ephesus (A.D. 431) and Chalcedon (A.D. 451).
The rejection of it is quite modern, often “throwing the baby out with the bathwater”, because non-Christians have tried to capitalize on it. And there are indeed some who also reject Christmas and Easter as Christian holidays, because others have tried to exploit them.
But in the final analysis, all are Christian celebrations, and more is lost than gained by rejecting them.