You're giving yourself WAAAAAAAAAAAAAAAAAYYYYYYYYYYYYYYYY too much credit.
Everyone knew streaming was eventually going to become what cable TV is. Cable TV started out with the very same promise streaming did.
But streaming isn't "unsustainable" or "going away." It's still way more profitable. They've cut out the middle man so to speak (although, Roku is the new middleman), they're getting significantly more money per subscriber, and they're getting your data.
Right now, they get to have their cake and eat it too. They're keeping their cable networks intact to keep that money coming in, even though these channels now only Bachelor knockoffs, reruns, and occassional live sporting events. They're also moving most of their content to streaming, and now they're getting advertiser revenue from it.
The only thing nobody could have predicted, which now seems likely, is the notion that ad-free plans might be done away with. I'm fully expecting every service, by 2026, to cost $20/month or more with ads.