True. However, because viral fatigue and related complications are generally present among symptomatic people (and 20-somethings are less symptomatic than other age-cohorts) it might well be that your risk of these things is also lower-- even if, conditioned on being symptomatic, the risk of "long-COVID" in 20-somethings is higher. I think the jury is still out regarding risk ratios for long-COVID, however-- partly because the pathology is rather ill-defined and still developing.

The more important point is just that viral fatigue and respiratory complications are not new things. They are present for a range of viruses. The mere existence of these factors is not pertinent to the "public good" point that the original comment centered on.