The problem with a subscription model, at least the straightforward one that newspapers use today, is that it encourages political echo chambers. If someone mainly reads, say, the New York Times (which I do), and tends to agree with Times editorials, they'd probably benefit from also reading the WSJ on occasion (both the news and the opinion section), if only to understand the "other side"'s point of view. But people already have a strong cognitive bias towards consuming media they agree with, rather than media that challenges their beliefs and makes them uncomfortable. So it'd be hard enough to attract such a person to the WSJ if it were free. Ask them to fork over hundreds of dollars, and only those with the greatest desire for neutrality (or just a ton of money to spare) will accept.
In my ideal world, I'd be able to pay for one subscription that gives me access to all the professional news outlets, and they'd split the fee based on how much time I spent reading articles on each site. (Time, not clicks, to avoid creating an incentive for clickbait headlines.) Or maybe some sort of micropayments system that's a similar idea but for the whole Web. But I don't see either happening anytime soon...