I believe OPs point is about considering the longer term effects. If we prevent a million Covid-19 deaths with a rushed vaccine, but the vaccine kills even a few people and brings anti-vaxx into full swing and we get a nationwide diphtheria outbreak instead, are we really coming out ahead?
Then again, the longer we wait to deploy a vaccine, the more likely a novel strain will emerge and make itself endemic and seasonal like the flu, in need of yearly vaccinations and persistently high CFR.