Interesting subject.
Let me first touch on those I don't pay. Factors include:
Greedy - Those I feel that drag their content out for the soul purpose of getting more money. Meaning updates are sparse or the content is miniumal.
Bad Content - This can go several ways
Story is bad
Renders are of poor quality
Choppy animations
Multiple games at one time - This is rather obvious. I have do have one creator I follow and Pay (Exception to the rule for me) but right now they're not working on the one the game that got me to subscribe to them in the first place.
Pay scale - Monthly to me is to much when you consider a normal full game is about $60 which if I pay $5 a month that works out except that in my experience with VNs that it take most creators at least 2 to 3 year to complete a well rounded VN. I personally would rather use itch.io an pay for a completed product or at the very least paying after deciding where or not I like the game. Al least I am only paying once. Good example, I Followed and played A Petal Amongst Thorns after the project was complete I bought the game off itch.io.
TRUST! - How many abandon games have we seen that were good. I understand circumstances and all but I don't want to give my money to something that may not even be completed.
Paid Bonus features - Like Gallery or other feature not in the game. Why not add loot crated too. If a person is subscribed or on discord there is probably a special teirs for special renders. I don't fell like there need to be a gallery of renders you have to pay for.
Too many creator I like - I pay 3 consistently but I also support others on Icth.io or through other means. I how ever would be broke if I pay everyone I liked.
I personally find that I support those that I am really into there content. That doesn't mean just seeing nude scenes. They have to have the ability to tell a story, even if is the same story just told in a different and unique way.
That is all I have for now.