Not only is tennis far more athletic - almost like fencing with a ball - it sounds and looks so much better. In tennis, the audible whack at the point of contact with the ball is so satisfying. Pickleball sounds, by contrast, are squeaky and annoying.
Pickleball is more accessible to new and older players, though. And that counts for something.
1. change: "high-level" -> "the highest professional levels". I'd wager Venus could play well easily until her 60s if not longer. There are many levels in tennis. There is are a range of competitive club levels. How often and how intensely she plays is another question.
2. Change: "the" -> "one" (w.r.t. "Pickleball is the sport she can still play.)
Stepping back, in my view, some of the most interesting questions are psychological and personal. If you were to talk to a hundred former tennis pros about aging, what would they say? How much do they play? How does it feel? How do they shift their mindset as their bodies age? To what degree is tennis still fun for them?