There absolutely is generic paracetamol, but we often colloquially use the word “tylenol” the same way y’all use “hoover.” It’s technically a brand, but we aren’t always referring to the brand - it’s just another noun sometimes.
In the case of RFK, I can’t explain if it was intentional to name the brand or if it’s simply one more thing he hasn’t applied that much critical thought to before speaking about.