So on one hand, you're saying that coronavirus is no big deal and that the flu needs to be taken more seriously. But on the other hand, you are criticizing the #1 remedy to the flu crisis (aside from basic hygiene). How the hell does that make any sense?
As far as the effectiveness goes, yes they sometimes miscalculate which strain of the flu is going to be the one that gets bad, but getting the shot is still better than nothing and should help boost your immunity.
As far as the "hazards" go, there is a far, FAR greater chance that you will be harmed from the flu than getting harmed from the vaccine. People who are immunocompromised especially cannot take that risk.
Flu shots are not perfect, and nobody is claiming that they are, but they are better than the alternative (getting seriously ill). And this is coming from someone who, admittedly, hasn't gotten the flu shot for a while, but in light of the pandemic, will be getting it going forward. Always take precautions.