Covid for my husband was about the same for when he had the flu in 2020 but he said the really bad part of covid was overall shorter than the flu but it lasted overall the same. A cold to him is less than the flu but for me it was about the same as my sinus infections except the fever with the flu that was not there with a sinus infection.
The covid vaccine side effects in various ways were worse overall than when I felt when I had the flu (same time as my husband), my fever was the same high level (103) and prolonged like when I had the flu but the nausea was so incredibly bad and my body felt worse, I bounced back faster when I had the flu (aside from the cough that didn't happen with the vaccine). For sinus infections the sinus pressure is so immense for me normally, my teeth hurt for days and days, along with muffled hearing. I didn't quite have that with the flu as badly as I have depending on the sinus infection, body aches were bad with the flu and I did throw up but the nausea with the covid vaccine was way worse in its punch. Flu, sinus infection, covid vaccine all knock me out just in slightly different ways, the flu I had (likely B as the person we were with the whole day tested as that) and sinus infections I usually have a lingering cough for a month to a month and a half, don't tend to get colds as it usually hits me as a sinus infections.
Because everyone's body is different it's hard to tell someone they must never have had the flu if they compared it to covid. Both IMO are serious things to pay attention to, that's where people focus when they compare them as if to shrug it off. I think that point is where you try to work with people's perception.