Same argument can be made against Woods in golf. I sure Jack or Arnie would have loved to have the clubs players use today.
While I definitely agree, there is another significant difference between contemporary and 'classic' sports hero records but it is outside the playing fields. These records that qualify for 'GOAT' status almost always are multinational and that means travel.
Modern travel, while still wearing, is also quicker and with lots of advice and methods for restoration to 'fighting condition'! The faster the travel, the more the contests one can play in. Ms Court, in her early years, probably traveled by ship more than airplane. While one could do exercises and ship travel is less stressful than by air, that has the tradeoff in time.
That wouldn't have changed a thing since they would have had to play against the other players using the same clubs.
Additionally, today's PGA is much deeper in talent than it was in Jack or Arnie's day as well as the courses becoming more difficult.