To speak more precisely, the first sale doctrines prevent the original seller from asserting intellectual property rights (copyright, patent, trademark) as a basis to prohibit resell. I was writing an internet comment, not a legal brief!
It's an obstacle to suing Doordash for trademark infringement, which is what you would typically do when someone is doing business in your name without your permission.
Yep! First sale doctrine applies to all transactions. This is why my gammy can resell her Oxy’s and it’s all nice and legal.