Let's be real, a lot of the blame does fall to Clint, not because he was the worst dad to ever exist, but he exposes how much a sniveling faggot he is via how he's dealt with Cobes adult life. Lots of people have kids who turn out to be useless junkies and there is nothing to be done and you've gotta cut ties because their a lost cause and you can't help them anyways, but Josh is a literal retard, and Clint has more power here then in your average shitty kid situation.
He clearly hit a point where he decided he was going to have minimal involvement, focus on his do-over family and focus his efforts on his own hedonistic fart smelling cringe art. remember the video where Clint is in tears because josh was playing San Andreas and he wouldn't stand for that kind of misogyny in his house, because you could beat virtual hookers or something, this is the sort of out of touch lib that Clint is, or aspires to be. He and josh really do share a lot of the same core driving forces, need for attention, delusions of grandeur, transparently performative art that's clear goal is to score pussy and gain clout, all while they think they've got everyone fooled into believe they have genuine passion and insight to share.
Clint has allowed Josh to fester a shit hole apartment, abuse drugs to the point of brain damage, have his teeth rot out of his head, all so he wouldn't have to deal with the nightmare that is trying to make Josh do anything. All while Josh is broadcasting his downfall for thousands of people to laugh at, for any normal parent that would be a serious wake up call they you need to do everything in your power to minimize the damage your mentally handicapped son is doing to himself. Josh was never going to be normal, but there was a path he could of dragged down, albeit kicking and screaming, where he was semi-functional, or at least not an active danger to himself, but Clint took the easy route,to focus on his pleasure and happiness, instead of doing the hard work to try and help water-headed idiot son. Clint isn't the worst man to ever live, but he is a fucking embarrassment, and deserves to be called on his bullshit. If you're going to give up on helping your retarded child, that's your choice, but you don't then get to take the credit and the easy route and cry online for pity.