The flu is different, because, generally speaking, when you are contagious with the flu, you know it. If you knowingly get on a flight while having flu symptoms, and someone dies because of it, you’ll pay a price. With CV19 you can be contagious and not even know you’ve been infected.
And if you have a negative test for Covid, assuming it’s a high quality test and is recent enough, that’s fine. That’s why all of these “passport” schemes also allow for testing out.
Life has a 100% mortality rate, but I wasn’t supposed to die today because some selfish ******* has to fly to see his sister-wife and won’t get a vaccine because ‘MURICA!