Another useful aspect of death as a metric, is that it is the most widely reported (as compared to, say, maximum fever, amount of ventilation required, days in hospital, lasting anosmia, etc. etc.)
For the overwhelming majority of people that is the only bad outcome. Severe conditions like ARDS are rare, but also correlate with Vitamin D deficiency even outside of the pandemic (https://pubmed.ncbi.nlm.nih.gov/25903964/). As for other symptoms that are being lumped together under the label “long COVID”, their incidence seems low, the severity is usually low, and nearly all conditions disappear over time. Some have suggested that perhaps those lingering effects are no different than a typical cold or flu, except this time we are all focused on this issue and noticing these things.
Personally I am not convinced that the young and heathy need to treat COVID specially. This is a pandemic of the old and unhealthy more than anything.
Polio was lethal in less than 1% of cases, and caused severe disability in a small fraction, too. Yet people didn't go into hysterics when asked to make a relatively larger sacrifice (the polio vaccine was far less safe than modern ones) for their country.
Death is useful as a metric because, unlike other health outcomes, particularly quality of life ones, there's no element of subjectivity.