Yeah, he's never been in good health. Heart murmur and everything. And I don't think he'd be remotely capable of the type of performances he used to put on even if he'd kept himself in good shape. But years of substance abuse made him way, way worse than I could ever have imagined.
I saw him opening for Slipknot last year (because my SO wanted to go, even though I tried to warn her), and the whole fucking arena was booing and calling for Slipknot after he fucked off for ten minutes at one point and the stage was silent. Came back, did an acceptable rendition of Sweet Dreams, and barely scraped his way through the rest. Managed maybe seven or eight songs off a ten-song setlist. Felt embarrassed for him.