I'm surprised at their conclusions, hadn't seen this article before. I found the crowds quite manageable but I guess it's also a relatively small area.
The picture is misleading. You can see that people are focussing on a person standing there. I guess a social media influencer entertained a visit to Vienna. The picture was taken on Graben street in the 1st city borough which is crowded with tourists, but not to that extent.
One has to be determined to see Vienna, the 1st District and whatever one wants regardless of the summer crowds if that in and of itself is no deterrent. The Stephanskirche is normally filled with tourists and tour groups , especially when 2 groups happen to arrive at the same time, but then so what? I go back to Vienna every summer , part and parcel of the trip's itinerary.