A realistic, non-hysterical analysis is that the virus will become entrenched in the community to the level of influenza at about a 1% fatality rate per case. But that would still mean killing up to 500,000 Americans per year vs the up to 50,000 per year for the flu (flu kills 1 in 1000 sufferers). The flu is the single-biggest killing disease in history. Sure, most people won't die but this new thing would have the ability to reduce average life expectancy a bit.
The new virus actually spreads more than the flu: the fact that "most people only get mild symptoms" is actually the dangerous thing about this. It ensures more people spread it. If a disease is stated as "within 48 hours you have bursting pustules then die instantly with your organs exploding!" then that's actually less of a worry. It's easy to contain that. Just stay away from the people with the exploding pustules. We won't be able to vaccine this away. Our vaccines don't work long-term for any other coronavirus, rhinovirus or the influenza virus, so yeah don't hold your breath.
"Just a worse flu" is saying "just worse ... than the single biggest killer in history". It's like hearing a new form of transport is 10 times less safe than driving a car, and saying "pfft, it's just a less-safe form of driving! How bad can it be? Everybody drives"