That's true, but we can still look at numbers to try to determine how. Otherwise, as conditions keep changing, we can conclude history has nothing to tell us and we should ignore all past data.
I don't expect anyone here to do a proper investigation, but if someone wanted to and pulled up the sales numbers for other franchises, we'd see if Shadows fit the same general trend of decreasing sales or if it's trending lower/higher.
We're not really going to though because there are too many variables out of our control. We can only accumulate different metrics and try to compare them fairly to accommodate variations in an attempt to determine general relative performance. Either people are free to present a piece of the puzzle and, pulling them all together from different pieces, draw up a picture, or we wait until someone somewhere investigates properly and present a full analysis.
AFAICS, Shadows definitely sold less than other titles, and notably different to the big sellers Odyssey and Valhalla. A decline of physical sales could account somewhat for that, which should be reflected across other titles. If digital was to account, given Shadows sales are less than half Valhalla's that launched in 2020, we should see a similar halving of sales numbers for other recent, comparable franchise releases.