The problem with this approach (not just for Reddit, but for all internet content sites) is that $9.99 is a significant investment when there are other sites providing content for free. The choice the user has to make isn't "Is Reddit worth $9.99?" but more like "Is Reddit better value at $9.99 than some other website at $0.00?", and Reddit is probably never going to win in that process for the majority of people.
It's the same reason why so few people sign up to pay for YouTube or Twitter. Video content is available elsewhere. Whatever the hell Twitter content is can be found just by talking to people.
On the other side so many do pay for Spotify and Netflix because that content is locked down pretty well. You can pirate some things, but it's a pain. Paying is easier.
Reddit seems to think it has a product that has value. Like so many web content hosts before it, it's probably wrong. It probably can't work as a business unless it's showing people adverts. And the problem with that model is that people hate adverts.
Honestly, until users realise that they can't have a content host unless they pay, no sites like Reddit will survive long term.
You'd probably get at most 5% signing up for the paid plan so the price would have to be more than 20x what they get from a free user seeing ads. Could work if they cut down the size of the organ but that has literally never happened
Also would force the platform into a death spiral. 95% of users leaving -> massive reduction in content -> more users leave -> no more content -> reddit is gone.
