Mmkay. You asked, though.
First and foremost, your writing in TS is too repetitive. A large portion of this comes from you mimicking Nasu's style, which is inherently very repetitive, although I can't fault you too much for that if it's what you find easiest to compose in. The content is what really hurts, though. Nearly every single post is the same stuff now, one of just a handful of different events:
1. Nanaya does something sleazy and does or does not get a little action out of it.
2. Nanaya makes a flamboyant gesture, usually due to some oddball choice, that goes far beyond what the choice indicated and makes him look stupid, then deals with the fallout.
3. Nanaya passes out or goes psycho and has a trippy dream/vision/something. (This one is especially bad. "Mysterious" and "symbolic" visions are hallmarks of a lazy writer and should be used extremely sparingly and only with good reason.)
Being stupid and flexing once, way back on Reimu route, was okay. Now, though, events like that are happening all the time. The fix for this is obvious - be more creative with events, and get a better handle on how you're writing Nanaya.
Beyond that, every single one of the non-Nanaya characters has exactly three and only three states of personality: lethal tsuntsun superbitch, sad deredere filled with unhappiness and finding solace in Naya, and prankster (comes in two subflavors, goofy or sly). They often switch between these emotional extremes at the drop of a hat. It should be obvious how to deal with this as well, though I understand it's hard to write varied characters.
Part of it may be due to the fact that we're on the fourth go-round, and you're very understandably getting burnt out, especially on writing characters you don't like. In the last playthrough, for example, it was really obvious that you ran flat out of material after the big fight and were left with no idea how to bridge the gap between that and the final conclusion. Again, there's no easy fix to be had, you like writing about certain characters and in certain ways, and that's fine, but trying to push the story back to your comfort zone when we've already been there many times is unsatisfying for the readers.
The second best advice I can give you, then, is to bite the bullet and be more creative. It need not be with new characters or psycho action or any specific thing, just do SOMETHING different and keep on doing different things instead of more of the same.
The best advice I can give, though, is to pay attention to your audience and play to them more. Listen not just to what people vote for, but what they actually want. If you can surprise them with something better than what they were hoping for, good, but if not, give them what they want.
Example: A lot of people got mad about the lack of Renko H and winding up mainly with Mary, but why? Because the entire story up to that point had been pointing towards Renko. She had the most points throughout, you said so yourself. Everyone accepted that this route was Renko route. We got right to the verge of an H-scene with her, before folks who were bored with the story spammed some stupid options. (It's worth noting that they were arguably not even stupid, as doing crazy things had produced decent results in the past!) Upon reset, suddenly, no more Renko, it's Reimu time bitches because YAF wants to write some Reimu. Then we pick to sit on the front steps, and suddenly Mary is all over Nanaya, and every set of choices from that point on were extremely biased towards Mary, with no real way to get to Renko. It's not that Renko is inherently a better character, but she was picked in the past, Anon came to terms with it and learned to like her, we wanted to finish her route, and then bam, the focus changes for no real reason.
Hopefully this will be somewhat helpful. A previous poster mentioned writing from different perspectives, and that would actually be a really good idea to practice using different styles and getting into other character's heads. You might, for instance, try to write that Renko H from her point of view, and say that she faked getting drunk so you can show off her personality a bit more.
Man, that came out longer than I thought it would. Might not be done, either, I'll post more if I think of anything else.