As a C# Developer using unity, at least I can say I have more experience making 3D games than 2D games. I really do enjoy making a visual novel because so much of it is basically UI development, data management and lots of figuring out things as you go. Of course it depends on how you go about it. Lots of Unity "devs" out here do use fungus and other libraries, and rightfully does get a bad rep, because they rarely even do write one line of code.
Would like to add that, I am always learning as I go, I never worked with visual novels before, but of course i have played some, so I am totally just figuring things out and do them like i want it to be, adding things i thought missing from other games etc, the coding is not that difficult per se if you look at general programming knowledge, but there are for sure components around the dialogue system and progression systems that can take a lot of thinking if you do it from scratch like I have, Later on the more you add, of course everything has to play well together too. Bigger game, more to test. I am having a blast, just like for artists, its a creative outlet for me. The feeling of developing new features with ease because i made the core flexible and strong, is an amazing feeling. and seeing people appreciate your hard work, that's really a motivator.
Some reasons for why we are using pre-rendered art, first of all it's the artist
2D / 3D Artists use completely different skillsets in many aspects, you can't for example render and then touch it up in photshop, its a completely different thing from making games in 3d, where you need realtime shaders, highly detailed textures etc.
Another huge reason for going 2D is the performance. Most people aren't neccesarily on gaming hardware. The kind of assets people use for 3d games are really hardware heavy, even if it doesnt look that good. Twist is one example.
Not only the performance but the quality too, you'll get the art like the artist envisioned it, most of the time. No compromises on texture quality, or lighting.
3d games is not that difficult to code, you are just working on one more dimention, depth. Most of the work comes into the animation, texturing, 3d modelling, this is generally not the work of the programmer. Someone makes the animation, the code then triggers the animation and plays it at appropriate speed, lots of work there but yeah...
3d games and drawn 2d games tend to have a lot in common though, once you set both up you can adapt the gameplay a lot based on what is already added previously. For example, you can reuse assets , change foreground and background combo for some variation, barely any work once its all in there.
with pre-rendered games, every render is a lot of damn work, unless you do the cutout approach similar to drawn-art games.