i think every holiday was invented to sell a bunch of stuff

I think there's some truth to that, especially when you look at how aggressively businesses commercialise holidays. But I wouldn't say companies invented them.

Most holidays have cultural, religious or historical roots that existed long before modern capitalism. Businesses simply recognised an opportunity and turned those traditions into marketing seasons. Christmas, Valentine's Day and even Mother's Day have become major commercial events.
The celebration itself isn't the problem; it's how consumerism has gradually become the centre of it. People should be able to celebrate without feeling pressured to spend money to prove their love, happiness or generosity.