The pundit, if I remember correctly, was Danny Murphy. What he meant was that we played an attractive brand of football that neutrals enjoyed watching. The fact that we regularly ended up beaten, even by fellow relegation strugglers, suggests a somewhat eccentric use of the word "best" -- particularly when you consider that the compliments about our brand of football were usually accompanied by comments to the effect that "Norwich leave themselves wide open" and "It's only a matter time before they concede". My definition of "best team ever to be relegated" would be something like "the team relegated by the narrowest ever margin, with the highest points total of any relegated team, having scored more goals and conceded fewer than any other team to suffer relegation". Our stats for the season don't bear any comparison to that.
Regarding what you say is one of the most credible reasons offered for our post-lockdown disaster, didn't every team face the same problem of recovering match fitness? But anyway, DF quite explicitly denied that our players were less fit than opposition players, Since he has the data I'm inclined to accept what he said.