He was never the best GK in the world, let's be real. A lot of English pundits either don't know much about European football or don't trust the British public to know about it. Oblak and Neuer, at the very least, are certainly better.
It's not like Alisson has a catalogue of memorable saves to back up his claim to being the best, either. He's like Ederson. Usually he just doesn't have much to do.
Hopefully the last of the people who still believed Alisson was anywhere near as good as Ederson with the ball at his feet have finally given up on that one, though.