What should they be using? If someone understands this crude metric as "If you catch it and you show symptoms and you test positive, your likelihood of dieing

What should they be using? If someone understands this crude metric as "If you catch it and you show symptoms and you test positive, your likelihood of dieing is roughly (deaths divided by confirmed cases)" then that seems reasonable to me. "Try to avoid catching it." is reasonable advice, as is "Be aware that you could catch it and be asymptomatic while still being infectious." to discourage people from visiting their grandparents this month. I don't feel like I'm being misinformed if I divide deaths by confirmed cases, I feel like I'm getting a rough worst-case estimate.