Your roadmap already has a plan to integrate a paid membership. But as far as I understand, it will take a long time to wait. What if you don't try to integrate buymeacoffee.com to speed up this process (before you implement a native payment system)? This system has the ability to accept both one-time and recurring payments. I saw that they have integration with Discord (to pay for channel membership), which means they probably have an API.
Another very important point (and I think many users will agree with me) is that completely hiding a certain category with a paid membership is not always a good idea. At the moment, you recommend using the integration capabilities of membership plugins for WordPress, but this method, as far as I understand, will also allow you to hide the paid category completely. But this method is bad in that all posts in a closed category will not be indexed by search engines and users, not seeing the post titles, in fact have to buy a pig in a poke.
What if you provide the ability to hide not the entire category completely, but only the content of the post (or even better, part of the content of the post, so that you can create some kind of introduction or preview)? See how it looks on the membership blogs on the buymeacoffee.com platform:
In general, I want to say that this outgoing year was very difficult and many people around the world are forced to look for a new type of activity or part-time work. Many experts in different fields want to put their knowledge to use, and a platform like yours can help build expert communities. If you roll out the paid membership features soon, I think it will explode in the popularity of your platform. So it might make sense for you to reconsider your priorities.