I think the magazine thing is just _wrong_, tbh; serialisation in magazines, as means of distributing novels, is dead. As you say, sci-fi, which used to be particularly heavily dependent on serialisation, has survived this. Litfic's problems lie elsewhere.
I think I agree with you: in the age of the internet, where you can 'sample' SF fiction on every corner, you may not need a middle-man (the SF magazine) going around collating those samples for you. You can find them on your own now! for free!