Unfortunately your assumptions are almost completely incorrect.
The reasons some get sick and die and others don't are multi(multi)factorial. There will be some genetic component, but also things like prior exposure to similar disease(s),socio-economic status, health status, age (this is a big one for COVID-19), all play into it.
The 1918 H1N1 influenza outbreak had a large number of confounding factors - it was in the middle of a global war, with large numbers of people (especially troops) crowding together (e.g. transport boats, barracks), often in terrible conditions (trenches), large portions of the world (esp. western Europe, China, Korea, parts of Africa) being refugees with poor nutrition, stress etc.
In addition it was at the very beginnings of modern medicine - there were no antibiotics to take care of the following bacterial infections, no supportive medicine, no respirators etc. 998
The people largely killed by the 1918 H1N1 were young men in their prime (20-40 y), who succumbed to something known as a cytokine storm, where their immune response was actually super strong (too strong) and they died from the resulting inflammation. There is a fairly large school of thought that says that the same is happening with COVID-19. It is thought that the cytokine storm against H1N1 is actually a heightened immune response because of prior exposure to another influenza virus. So, these people actually have "good" immune genes, but were the ones killed off by the virus.
Secondly - "just search for poor genes" - you are advocating for something that a) we don't yet know all the genes involved in immune responses, and b) segregation of the population based on genetic characteristics (now where have I heard of that happening before...here, here, here); might have some sort of impingement on things like human rights, especially when you consider that age is one of the largest factors for COVID-19 death.
Now those 3 comparisons above are a lot shitty, because those were horrific things done with no just cause, and you could make an argument that those more at risk of COVID-19 should take more precautions (as many do) - but how do you enact that into law? How do you enforce it? Can you tell if someone walking down the street has diabetes or asthma and are thus more at risk? 225