By who?
People who minmaxed and saturated themself by making 3-5 naxxgeared characters and hording 100k+ gold? By thoose who played classic everyday for hours the past 2 years? By the people who do not care about the game but love to defend blizzard or love to hate on people enjoying other games?
Theres still enough people technically. They are just spread across to many servers. Not only that, but these artificially made “empty” servers do not allow for a healthy impression towards new players, who will thus less likely play on any of them which in turn does not allow for the problem to fix itself.