As described here, this is just Weird Scrupulosity Thanksgiving. Which is about as likely to get anyone to enjoy it as Newtonmas. It will be an obligation to some people, a thing done to indulge friends by their friends, and ignored by everyone else.
If you want a harvest holiday that is not Thanksgiving, don't structure it like or at the same time of year as Thanksgiving. August, the equinox, and November are all historically appropriate as harvest festival times; two of the three are open in modern secular-cosmopolitan society.