Yes, they unfairly are judged. This criticism seems to come from people who very much likely have not played the games/series they are criticizing and rather see the same character and make assumptions. It's not like they really milk any series. 1 mariokart, 1 smash bros, 2 3d marios with a 3 year lapse, 1 2d mario, 2 radically different kirby games, 2 extremely different metroid games, 1 DKC game, 1 Fire Emblem, 1 Paper Mario, etc. 1 to 2 titles in a series every gen keeps the series from getting stale even if they only add minimal upgrades imo.
"Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth." -My good friend Mark Aurelius