You can see what happens without containment in Sweden. Given that countries with a bad health system probably need more measures.
The real difference is that we are informed broadly about the many deaths and this was not the case with the flu in our lifetime.
The flu kills a lot of people over a long time, this is 500k in just a few months while everyone is actively trying to avoid spreading it. The flu definitely does not kill more than that.
https://www.cdc.gov/flu/about/season/flu-season.htm
The exact timing and duration of flu seasons can vary, but influenza activity often begins to increase in October. Most of the time flu activity peaks between December and February, although activity can last as late as May.
It also does NOT kill Millions of people per season
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815659/
Until recently, the World Health Organization (WHO) estimated the annual mortality burden of influenza to be 250 000 to 500 000 all-cause deaths globally; however, a 2017 study indicated a substantially higher mortality burden, at 290 000-650 000 influenza-associated deaths from respiratory causes alone