This is something I was worried about too and this is kind of where the potential concern of toxicity among creators comes up. If Tapas were to implement a system like this, it's only a matter of time before I start getting bombarded with messages from fans going "I would love to support you, but creator x, y and z have rape in their comics and I refuse to support that". Now this may not be a concern to some people reading this, as I know quite a few who would do anything to get content with rape in it away from the site, but what if I applied this same scenario to other content? Because similarily, creators who make straight romance or other genres might have fans approaching them going "I would love to support you but creators a, b and c have gay and trans characters in their comics and I refuse to support that". This would run the risk of raising concerns of what creative choices should be muffled or removed entirely rather than left up to the individual consumer to read or reject, because all of a sudden every single creative choice any premium creator makes will immediately affect all other creators, in a way it currently doesn't do.
This would be a dangerous setup for animosity between creators. While I believe myself and most of my fellow premium creators are mature enough to not get into petty drama, this does not go for some fans. If a system like this were to be implemented, I would fear the day that fans start harrassing creators they think should leave the platform so they can feel morally just in buying a subscription. Regardless of what those moral intentions are, it would create a generally toxic environment.
If Tapas wants to be a platform that focuses on the creator, is personal in nature (as it is, with creator profiles and communication tools at the fingertips of the fans and creators alike), and still be open to a wide variety of creators, a subscription system isn't going to work.
It works on Amazon, Netflix etc without these problems because those platforms are impersonal and very large. The concern of "what if some of my money goes to a creator whose content goes against my moral judgement" doesn't cross the consumer's mind as much when that is the case.