Not really. If you want to convince people that COVID-19 is significantly different the seasonal flu, all you have to do is compare COVID-19's ~500k death toll

Not really. If you want to convince people that COVID-19 is significantly different the seasonal flu, all you have to do is compare COVID-19's ~500k death toll in 2020 to the flu's ~50k average death toll for recent years. That said, I haven't heard of anyone using the "just the flu" argument since the first couple months of the pandemic.