In a vacuum this isn't true: diseases will select to be more transmissible, that can mean less deadly, but not always, think HIV. If the incubation time is long enough before death, then it could not matter. So, you could imagine a nightmare scenario where some disease selects to have a longer incubation time while still transmitting, but then causes more severe disease down the road.
However, because we have vaccines, I do think ultimately you're right. If it turns out that omicron (or another variant) is basically a cold but also evades current vaccines, I think society will 'allow' it to become endemic.
However, because we have vaccines, I do think ultimately you're right. If it turns out that omicron (or another variant) is basically a cold but also evades current vaccines, I think society will 'allow' it to become endemic.