the whole point is “giving thanks”!
I would personally thank all the various farmers if they happened to be gathered in my dining room, but that doesn't tend to happen very often.
Nobody has to be there physically; in fact the main point is to give thanks for the arrival of the Puritans/your particular immigrant ancestors/the European colonization of the Americas generally, since you would not be enjoying the holiday if that had not happened.
Is that the main point?
Interesting tidbit of trivia: the first proclamation of an annual day of thanksgiving was made by Abraham Lincoln in 1863; it didn’t mention the pilgrims.
Thanksgiving is a foreign Yankee imposition; it wasn’t even regularly celebrated in the South until the turn of the century. We prefer our grand Easter and Christmas dinners (something the Puritans would shudder at.)