I'll start by saying I compeletely disagree with categorizing Dark as a player who had only found success in a dead game. He's been competing since late WoL, reached semis+ in 2015 3 times, and won tournaments in 2016. So imo he definitely deserves a top 10 on GOAT list.
That being said, I do agree that players who peaked later and found success ONLY in a dead scene should not be considered as highly in terms of GOAT status. A player that comes to mind is TY (and similarly Rogue), who only started winning premiers in start of 2017; and I'm happy to see that reflected with a relatively low ranking. 1 Year is a huge amount of time in esports, and compared to dark's 2016 premier wins, these should be considered less valuable.
Likewise, if you win your first premier in like 2018 AND demonstrated you're trash when the game was competitive, you're pretty much out of contention for GOAT as your resume can't hold a candle to people who actually competed in an alive game.
All in all I'm really happy to see Mizenhauer take this criteria into consideration when constructing his GOAT list. It's just a shame he misjudged Dark.