Christian Bale told an interviewer that he's excited for Joaquin Phoenix because

I’m so sick of people only associating Heath Ledger with Joker. That role didn’t kill him (he was using a plethora of drugs) and It wasn’t even his last movie (Imaginarium of Dr Parnasas was) ... so how tf is it brave for an actor to act in a role he was paid handsomely for?

First I’d like to say that personally I don’t think that joker version was definitive or even defining of the character. It was well acted for sure. But I sometimes feel like well meaning people (and perhaps some not so well meaning) who try to respect the actor actually disrespect them. Ledgers death was mystified and tied tightly to his performance as the joker (certainly a nice added bit of publicity, and its much harder to even legitimately and gently critique the acting of a dead man- especially when his death has basically been made part of the performance. The well meaning exaltation of his performance and conflation with his death often turns a tragic suicide into a piece of performance art. But to each their own.