I'll take the first stab at that, if nobody minds.
You're right. We can't estimate the actual percentage. Right now all we have to go by is waste-water surveillance to estimate the rates in the population at this point. I would suspect, from modelling data, that it probably is close to 30% of the population who have been infected now.
I don't think the percentage is the important point. It is the severity of the cases that we see and the number, in the end. I say this because we can all agree that if 10 million people were infected, then the impact on society would be quite devastating. I don't like to be a doomsayer; I'm always on the side of someone who says, I think it's not as bad as we all think it is. But in particular, I look at severe cardiovascular events and also these cognitive impairments. That, to me, is the gravest concern. We struggle already in our health care system in dealing with dementia, Alzheimer's and Parkinson's. I think that's where the difficulties lie.
The last point I'll make is that I had it. I'm not one, as well, to acknowledge symptoms, but I was out for at least a month and a half, and that was with delta. That was prior to my ability to get vaccinated; it was too early for me. It took me quite a long time to recover, and I still have some minor effects. Now, is it debilitating? No, not for me. I had to do a pretty busy work schedule. But if it is mild, in my case I can see how it could be more severe in others. That's anecdotal.