Lets look at the reasons why the situation is different.
Many use the argument that influenza was so deadly in 1918 that it had to become more infectious and milder just to keep spreading. If this were the case, you'd expect influenza to currently have very high levels of transmission in these 'mild' variants we would have today.
This never happened. Influenza has a very low transmission rate of r0 of 1.5 to 3. Sars2 is now r0 > 12 at minimum and higher than measles (18) at maximum.