By way of explanation,,, COPD is "chronic obstructive pulmonary disease" but one person may have emphysema another might have asthma(but rare) chronic bronchitis,inhalation of chemicals ect. the point is though that all though all of these fall under the heading COPD there are different approaches to treating them because they are caused by different things.
And in the same thought "influenza" (Flu) in one thing while Corona-virus is another "thing". Both of the two attack the respiratory system and have some similar symptoms but also different symptoms because they are different "things". Because they are different "things/disease's" they are treated differently and are mitigated differently.
You have caught the seasonal flu probably multiple times without having longtime damage to your organs here is a link to what they are finding in patients who from C-19 (first one I grabbed there are others if you do a search on www)
https://www.advisory.com/daily-briefing/2020/07/14/covid-autopsies In C-19 patients one of the symptoms that stands out differently from the common flu is the "blood clotting".
Now if you read the link and others you find then you'll realize that whats happening to those who become infected with C-19 is that their blood begins to "clot" in their veins as it's circulating through their circulatory system. These clots then become lodged in different places, lungs,brain,kidney,liver ect. and since the blood flow then is restricted to that "spot" it no longer receives oxygen/nutrition and so that "spot" dies.
Some people recover from C-19 without any problems because the clotting did not advance as much or at all. In others when they recover they may have holes where the clots killed spots in their lungs or maybe kidney,liver brain ect... So sometimes they may recover and have respiratory damage or not or only slight damage(100 percent lung function reduced to 80 percent) or worse. Some may have kidney damage others neurological damage but everyone's a little different in degree of damage.
So then unlike the seasonal flu where you catch it and this isn't the issue catching C-19 multiple times will/could "create it's own preexisting health conditions". So if you catch it and you recover but have 10 percent organ damage then since your body has preexisting health conditions caused by a prior infection with C-19 when you recover again it will cause more organ damage. So catching it over and over will eventually do the same thing it does to those with compromised health issues(fatal) but some people will catch it multiple times before their organs are that compromised.