I would say that things already demonstrately got terrible. The mining landscape is very centralized, with apparently a majority depending on agreements to trust each other's announced blocks without validation.
I believe that if the above would have happened overnight, people would have cried wolf. But somehow it happened slow enough, and "things kept working".
I don't think that this is a good criterion. Bitcoin can "work" with gigabyte blocks today, if everyone uses the same few blockchain validation services, the same few online wallets, and mining is done by a cartel that only allows joining after signing a contract so they can sue you if you create an invalid block. Do you think people will then agree that "things got demonstratebly worse"?
Don't turn Bitcoin into something uninteresting, please.