Batman and the Joker have perhaps the most complicated dynamic in all of comics -- and it's clear that they need each other more than they admit. Joker has caused Batman and many others lots of pain. Any suggestion that Batman "needs" the man who killed his son is absurd.
Batman doesn't need to fight crime to validate himself, and he especially doesn't need to fight Joker to validate himself. Joker on the other hand definitely needs Batman to a pretty large degree. However, during this time, Joker's real reason for wanting to torture Batman wasn't really elaborated on all that much.
Some people think Joker wants to kill Batman and destroy Gotham, some people think Joker wants Batman to kill him in order to break Batman's one rule. But the actual truth of what the Joker wants is just a bit more complicated. One creative way to build to a Batman-Joker showdown is to introduce the villain in his own spinoff project, either a streaming series on HBO Max or another feature film.
Would the Joker still be the same without Batman? Explore the deep connection between the Clown Prince of Crime and the Dark Knight, analyzing if Joker could exist without his greatest nemesis. What's the deal with Batman and the Joker? On a surface level their relationship is simple. You could ask any preschooler who has ever watched a Batman cartoon and they'll tell you simply that Batman is the hero and Joker is the villain.
Does Joker care if he dies? The Joker's relationship with death isn't about fear; it's about performance. His nihilistic worldview frames mortality as the ultimate punchline, a grand finale to his chaotic masterpiece. He doesn't fear death itself, but a meaningless one.
This highlights a crucial character trait: his profound need for. Batman has one of the deepest rogues galleries of villains, so why do we keep going back to the same Big Bads over and over again? "Joker and the Batman need/complete each other." Noooo, if Joker dies,Batman still has Riddler,Two-Face,Clayface,Bane,Killer Croc,etc and doesn't look any sleep over Joker's death. Meanwhile Joker's ass gets frantic and depressed when Batman dies/ignores him.
Batman doesn't need Joker, Joker needs Batman. You're suggesting that Batman needs Joker to improve his detective skills, but Joker's livelihood has killed thousands of people.