Slow? You got to be joking.. Pickleball is a high intensity and strategic game. Is a sport that requires fast hands, reflexes and deadly accuracy to hit a third shot drop to the kitchen zone (near to net). Watch this video and you will find out
Tennis is very generic game, mostly about driving the ball with groundstrokes, occasionally volley and drop shot, that's about it. There is hardly any spin in tennis, spin I mean from ball spin sideways, not topspin or backspin only. It's mainly demads physical power, speed and stamina, which is why not many short players are high ranked.
Badminton very generic too, just make opponent run around the court and the shuttle can't even bounce.
Pickleball is a variation of tennis, table tennis and badminton. All the skills including 1) driving (tennis) 2) ball spin (table tennis) and 3) dinking / net play (badminton) are applied. The kitchen or non-volley zone adds a layer of complexity and challenge to pickleball.