If you're assuming one person is working on the whole thing, this is everything that needs to be done:
- Writing (outline and script)
- Base Imaging (DAZ, HS2, KK, etc.)
- Post processing (PhotoShop, Paint.NET, etc.)
- Animation (various programs)
- Coding/Assembly (using Unreal/Ren'py/RPGM/etc.)
- Distribution (sending it out to sites like LC)
- Social Media & Advertisement (Discord, Reddit, Twitter, etc.)
The sheer amount of stuff that has to be Top A+ Level to get to a SSP or other similar game is enormous. Then, add in all the competition and the fact certain genres have a low amount of devs due to laws and such...
Very, very few devs can reach that level in every category. The best thing you can do is lower expectations slightly. Don't mean play stuff that doesn't look good at all, but to just give it a try. Even though I'm not a fan of NTR and I'm not into DAZ characters, I thoroughly enjoyed F Kingdom.