First, you need to know how to make a 2d or 3d grid movement system.....
We know how to make a Roguelike, even if you don't you will have tutorials up the wazoo for whatever engine you want.
There are game jams specifically for roguelikes so the very basic gameplay is a non-issue.
You need to get the tiles. You need to make them into prefabs so that the game can know to use them as building blocks for the level. (Just this can be several hours of work, because no, getting art assets is not a magically easy process, and even if you just use placeholders, you still need to make them recognisable, so you would need to have some design of the different elements of the dungeon done, and then you would need to art something that looks reasonably close to what you want, so that it is recognisable)
Yes getting the Tileset is something you have to figure it out yourself. And tend to need Higher Rez than your typical 32x32 as that wouldn't work with the Rendered Sprites that well.
Worse case you can make them yourself and use something like
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as Raytraced Rendered Voxels can work well with Rendered Sprites.
There are a lot of skills in ES2. I think I've seen about 12 to 15 of them, and that is a decent number to make, for certain, especially since they are quite varied, from basic skills that just improve your stats, to passive skills that add you a unique modifier such as a chance to heal on getting hit, or an auto-attack each time you attack, to actual targeted skill, with a targeting UI.
Also known as "the fun", you would need to have no creative bone in your body to not do something here, and even then creativity is optional and you can just clone the better games.
And a Porn Game doesn't have that high of a standard like Indie Games that live and die completely on their gameplay.
Let's talk about the cutscenes. All of them are fully animated, with a decent amount of text and they are fully voiced. So, someone needs to write a scenario for each of these cutscenes (well, they're mostly sex scenes, but whatever), then once you've written it, we need to get assets for the environment, as well as character and monster assets. Let's say we use Koikatsu for this. Just finding a map that fits is going to take you like half an hour, because the selection is not that ample. Once you find it, you will probably take 10 to 20 minutes to find a model for your monster.
In KK, the monster models just have some bones that you manipulate and they dont have premade poses or premade animations. So, you're going to need to pose your character, pose the monster, and probably replace the monster dick with an object dick, because if you don't do that, animating the shit is going to be a nightmare.
I completely agree, but this isn't a new problem, this is what you have to do in your regular AVN here. If this was a real problem this Industry wouldn't exist.
And the content requirements are much more modest.
How many sex scenes total does those games have?
Even if you manage to finish the project, you still need to deal with a lot of bugs that will crop up at this stage, because as a one-man dev team, no matter how much you playtested your game, you haven't had hundred of hours to do it, and there are almost certainely some scenarios that you have not had the chance to experience. And if you haven't had the chance to experience them, it is likely that there are still bugs, even if you've been dilligently eliminating any bugs that you found. So you need a playtesting phase, and probably a whole lot of time to fix bugs.
It would be the same Early Access and Patreon Model just like any game here, you can expanded the content with new dungeons, new enemies, new skills, etc. all the while you fix things and polish stuff.