Remember that this isn't meant to be connected to the DCEU at all. The Joker's still there in Birds of Prey, though I forget if they're keeping Leto specifically around or not.
This is an Elseworlds one-shot.
I thought it was brilliant. Uncomfortable, sure, but to me the discomfort came off as guided, deliberate, and impactful. It's a really great take on the Joker, too, a man who is at once completely monstrous and yet a victim of circumstance, like the most compelling of the Bat-villains, a truly tragic figure who could not have turned out any other way (albeit driven there by Diablos Ex Machina, like many of the Rogues Gallery, such as with his social worker getting cut off and thus cutting access to his anti-psychotics).
I really enjoyed the questionable reality of all of it, particularly the question of his paternity. A theory my friend and I came up with on leaving was that the "deal" that Thomas Wayne struck was to get Arthur back in Penny's custody, in exchange for forging papers of his adoption. And the cool thing is that could be true, or not! It doesn't matter and is just a fractal bouncing through the corridor of Joker's mind.