IFR could be calculated only from the explanation only at the final screen, where the actual number of infections is estimated (it's several times higher than the confirmed cases)
We could legitimately say that in your game, the number of infected people was not 2.1M, but, including reinfections, there were up to 6.2M infections, according to experts’ theories. The game and your results only register the officially recorded infections (based on test data).
Taking in data present today and looking at countries that are doing nothing (Sweden), their total population death rate isn't as high as 4% either.
Do you have a source?
I'm not fooling myself with precision so I concluded roughly 5%.
An interesting note after the fact that the early estimated US deathrate of 1.9% tracks modern data pretty well [2] which is 1.8% (605,792/33,769,600).
[1] Sources and math, I used archive.org to get the numbers from March 2020 https://www.worldometers.info/coronavirus/coronavirus-age-se...) https://www.census.gov/data/tables/2019/demo/age-and-sex/201... age-sex-composition.html
age pop(M) deathrate theoretical-deaths
00-39 169.5 0.2% 0.34
40-49 39.9 0.4% 0.16
50-59 41.5 1.3% 0.54
60-69 37.9 3.6% 1.36
70-79 23.4 8.0% 1.87
80+ 11.9 14.8% 1.76
----------------------------
total 324.1 6.04
6/324.1 = 1.9%
[2] https://gis.cdc.gov/grasp/COVIDNet/COVID19_5.html[3] https://www.nytimes.com/interactive/2021/us/covid-cases-deat...