I'll put my response in here as I'm currently developing some game titles myself, I may not be the best or the fastest when it comes to the coding part of the games, but my artworks have come on leaps and bounds. However, my main strength when developing these games is that I can tell a story and very often with so many adult games the first three things complained about very often by most players are
1) The pacing of the story is always criticised as terms used often are where devs "milk their patrons" or go hell for leather where the pace is fast to steady then it seems that the dev either gets bored or runs out of ideas, hence popular games ending up on the abandoned list.
2) The Lack of plot and any logical sense when it comes to writing a story as it's either all over the place or unreadable (maybe this could be that many devs these days are from different countries where English is their second language and Google Translate is usually not very helpful in the real world).
3) Character development (and probably to me the most important one), now I totally agree that there is no magic penis in this world that makes women just fall in love and jump you in real life and the fact that in some incest driven games the focus is "wow brother (or son) your cock is so huge, do you mind if I sit on it". Other plot lines include the female characters being extremely shallow (money is the key point I'm trying to make here), buy the girls enough gifts and they fall in bed with you no matter what relation they are to the MC. Here is where realistic psychology is utilised better, I'd advise anyone to put themselves in the situation and ask "how would I react??".
My best responses here to the main problems for adult games (my own personal opinions, not meant to offend), and how to overcome boundaries and plot holes. Some may like this others won't.
1) To get a perfectly paced game, with an equal amount of build to payoff I'd recommend using as many characters as possible (this is what I am doing right now). Each character in the game has to have their own personality traits ranging from "Slutty" to "Shy Virgin" and display these traits in the story. Something that helps with this gameplay speaking is by having stats for the main character, as different females have different traits that they are attracted to like for example sense of humour, a fit athletic body, intelligence, kindness, the list goes on. However, this type of game has a fine line between being "too easy" and being "grindy" and it's up to the developer to find a happy medium between these two fine lines which can be really tough, it's pretty much trial and error.
2) The plot is very important to any game so my best advice would be to create a small but decent back story for the main character, then write the beginning of the game, then next write in the end of the game and where the main character is going to end up. The fun part is then writing in the middle part, taking into account backstory, the beginning and the end and how the main character gets to where he/she needs to be. Simplified down to the simple 4 rules for writing any kind of story is a) Short Backstory b) Beginning of the story c) end of the story d) the journey from beginning to end. This is the best way I can explain. Repeat this process for the majority of characters in the game and you're half way there to being a winner, winner, chicken dinner lol.
3) Character development - This can easily be overcome by following the points I placed in the above two points. Develop the main characters stats as in the real world there is no magical potion that makes anyone of the opposite sex instantly want to bounce on you just after having one conversation. The idea with the stats is that once maxed out you then have a MC that is potentially the hottest guy in the game, which then makes it more believable if the girls all swoon at your feet. Next, by using the abcd method I mentioned in 2) by duplicating this process for all the other characters of the game then it will automatically help with character development as well as plot and these go hand in hand, you can essentially kill off two birds with one stone, hence less development work later on if everything is planned out beforehand.
Just to summarise
1) Use as many characters as possible and give each character a difficulty level in your development plan to get to the final goal with.
2) Character development and plot can go hand in hand by using the abcd method I explained above.
3) Base the game logic in reality, not the clichéd low budget Skinemax movie logic.
4) Stats are a good thing
5) Having an antagonist or a rival in the game can be a good thing just don't make him/her an Eric. What I mean by this is to give the player an opportunity to overcome the villain at every turn, not to be cucked at every turn.
6) Use some extreme fetishes in the game but warn players beforehand what fetishes will be shown when undertaking each quest (so you can put in M/M, NTR and others without offending gamers if they are warned first). Also make these side quests optional.