Alternative interpretation: Google so useful that it instantly searches whatever sub-corpus you desire if you simply mention it in your question.
Google says it shows zero ads on 80% of searches. So the whole "ads now take up entire screen" thing is based on the qualitative ramblings of twitter accounts who don't know what they are talking about.
I think part of this is the inverse of the base rate fallacy. As people's use of search has gone up, the absolute number of bad experience (many ads, or poor results) has gone up regardless of whether the actual quality had gone up or not. Combine that with the elevated expectation and the confirmation bias, some people's perception of search quality will get worse and the number of people with such opinion will increase.
Google says it shows zero ads on 80% of searches. So the whole "ads now take up entire screen" thing is based on the qualitative ramblings of twitter accounts who don't know what they are talking about.