I’m not going to be doing group rides anytime soon. In the draft you are literally in the aerosolized slipstream of the heavy breathing rider in front of you. Doing this for a two hour ride has the potential to expose you to a heavy viral load.
Conversely, riding by yourself, even with other cyclists and pedestrians around you, you may be exposed very briefly to micro droplets. But you’re moving past them quickly, and the odds of getting a viral load sufficient to cause infection are remote.
This fluid analysis indicates that if you’re following a bicycle at speed you may need to be 20 meters behind.
https://science4performance.com/tag/covid-19
I think that’s likely too extreme, but the point is the needed distance to be safe, eliminates any drafting effect, and would make a group ride of any size unmanageably long.