The solution is you release shows and give subscribers access to them based on if they were subbed for long enough for the season
That is ~a~ solution, but I don't think it would work.
People want to see the current thing so they can talk about it around the water cooler. If you are a few episodes back, you don't get in on the conversation. If you play the reverse and don't let them catch up on later episodes until they are caught up on sub time, then you have lost all context and back story for the current episodes. It breaks down either way you look a it.
There are 2 good solutions I see, neither are new though.
One way Disney and HBO (and others) do it now, and regular TV has done since it's existence - drizzle the stuff out slowly. That keeps people subscribed until the end of the season at least - and in the case of Hulu you could only catch up on the older stuff if you paid more. The big gaps in between seasons, and these short 8 or 10 episode seasons are bullshit and hurting the streaming services, as you got to have something to fill the gaps to keep people subscribed; not even Disney has enough running current shows to do that right now.
The other way to counter people dropping subs is to offer good deals on long term subscriptions.. the discounts on 6 mon and 1 year plans. Disney and HBO both do this; Netflix doesn't. Sure, you "lose" out on some revenue, but you don't see those massive swings in subscriber counts as your big name shows hit and roll off.
A potential third solution would be Amazon's approach (Apple started it, but has kinda pulled away from it) - let people just purchase a single show, rather than sub the entire channel. It often costs just about as much as subscribing, but you don't have to deal with remembering to cancel the subscription; it's just a flat cost, you get access to the show as it comes out. I've done this with a handful of things, and the second benefit is you don't have to have login credentials for multiple streaming services to use it.