By that, I presume you mean sit back and do nothing, and let 'immunity' arise from infections.

That doesn't work with Covid because the mortality rate is too high and the infection rate leads to healthcare being overwhelmed.

If there was evidence that the mortality rate was low (but we have evidence of the opposite) or that the infection rate didn't spike upwards and start clogging up the beds that hospitals have which are able to deal with Covid (but we have evidence of the opposite), then that might be a conclusion that would permit proposing it. But we have direct evidence of the opposite.

It will work fine for younger populations though.

Young populations are not hermetically sealed away from older populations.

And even then, some of the young deaths have been horrific - e.g. the blood-drenched walls from the 13 year old who died, see https://www.thesun.co.uk/news/13519684/shock-photos-blood-bo...