We're in a golden age of television in part because everyone is producing high-quality shows. For every Deadwood, there's a Justified; True Detective, a Mindhunter. HBO has never been the best place for comedy series and, good as Crashing was, it remains an also-ran there as well.
HBO's quality has been pretty far off its peak for awhile. GoT is a tentpole show with a rabid audience but it's not especially good (it's no The Wire). Deadwood and the Sopranos are from a different era of TV. Veep is great, but True Detective, True Blood, Boardwalk Empire, Enlightened, and The Newsroom would all be in the middle of the pack at Netflix.
More importantly than what Netflix itself creates is the fact that everyone else is creating great TV, and Netflix can just license it. The Americans is better than anything HBO ever produced except The Wire, and it's an FX show. So are Atlanta and Better Things, both better than any HBO comedy series other than Veep. AMC has Breaking Bad and Better Call Saul, which arguably are the best thing ever done on TV.
The Deuce is great, but if I have to choose between paying for one show of that caliber per month, or just getting access to stuff like Counterpart, Legion, Get Shorty, Halt and Catch Fire, and Fargo, it's pretty obvious where I'm getting my money's worth.
Which is the big dilemma with HBO's previous strategy. There is too much content that clears the bar HBO set available outside of HBO for them to charge a premium, unless they can keep bottling lightning like they did with GoT, which is not at all a sure bet.