From a symptoms and virology standpoint, COVID-19 is closer to being like a really really bad cold. Several of the people I know who had it literally used those words to describe their experience. Several other endemic human coronaviruses also cause colds.
But surely, the hundreds of thousands of dead in the US alone, millions worldwide, would suggest that while for many people it is a really really bad cold, for others it is far worse than the flu?
You're missing the point. The SARS-CoV-2 virus is almost completely different from the influenza virus. It's structurally much closer to at least some cold viruses. In particular it's very similar to HCoV-OC43 which causes colds and frequently kills patients who are in poor health to start with.
