Court, Navratilova, Evert all had long great careers without the exorbitant amounts of cash thrown at the Williams sisters.
The era in which Serena dominated did not include any other all time greats (just imagine how many Navratilova or Every would have won if not for the other).
Williams never had to play in 25 tournament in a year because and risk the wear and tear on her body that the players in earlier eras did because there was not money.
ESPN and other sports carriers decided a couple of decades ago to push only modern players with easily clipped highlights could even be in the discussion of GOAT... Earlier tennis players. Basketball, etc are long forgotten.
That Wilt averaged 50 points and 20 rebounds a game for several seasons ... doesn't matter. Or that Russell has almost twice as many rings as Jordan. That Martina Navratilova consistently was in the semis of both singles and doubles at every major for over a decade (and sometimes mixed doubles too) is ignored.
Margaret Court is an old woman who has beliefs about LGBTQ+ that I completely disagree with. But, she was one of the greatest and to not admit that ignores the history of the sport.
(Tennis magazine did an interesting study on rackets of different eras, they found that you could hit the ball virtually the same speed with wooden or metal rackets, but that the sweet spots were much. Much smaller than the modern rackets. Would be interesting to see how a big hitter like Williams not known for accuracy would have fared with a tiny sweet spot wooden racket.