I've been working in the VN space for over a decade now as both an avid hobbyist and professional software engineer. There is an immense swath of incredible content out there, all made by gorgeous human hands. In recent years, developers like me have asked the question: "What benefits are there to AI tools?"
AI-generated content for visual novels have a lot of pros and cons, such as:
Pros:
Easier for low or no-budget developers to create art assets
Some developers prefer doing things on their own, or lack the funds required to commission the amount of content required for a full-fledged VN. Sprites, backgrounds, and CGs are typically the bulk of the artwork required for a VN of any scope, and being able to quickly generate some of them saves money and time. Done well, you can create some impressive-looking backgrounds and CGs using pure prompting, overlaying a preexisting image, or a hybrid of both.
Similarly, developers can use AI generated content as a means to get placeholder assets in-game quickly, and can be used as part of a demo, game jam, or beta version until the real assets can be created.
AI image upscaling allows for resizing of images
Probably the easiest and simplest usage of AI. Very useful if you need to scale an image to a different size for zooms or pans.
Cons:
AI-generated writing is typically of poor quality
There's no real comparison -- human-led writing is still leagues better than what current LLMs can output, and avid VN readers will be able to quickly sniff out an AI-generated eroge route.
AI-generated music and voice acting is also of poor quality
Once again, real human creativity shines through here. AI-generated voices are often flat and monotone, and music is similarly mechanical in both tone and sound.
AI models often contain copyrighted/unauthorized work
The ethics involved here make it difficult to really justify AI-generated content for commercial works. Most models available now often have art taken from social media or from platforms like Patreon, Pixiv, or Fantia without the artist's permission.
Other questions that developers have talked about:
Will AI tools cause some artists to get less work/be out of a job?
Yes, it's entirely possible that some artists will find it hard to compete with more advanced iterations of AI art models. Whether due to quality or quantity, some artists have become disheartened by the proliferation of AI as a means to an end. There are solutions to this (better self-advertising, seeking out paid work on job sites, etc.) but that is on the artist to learn.
Will AI tools increase the amount of visual novels released?
Most certainly. However, that doesn't mean that they'll be at Tsukihime or Stein's;Gate levels of quality. Truly stand-out titles work because of good marketing, a good response from the consumer base, and most importantly, good content. 100 AI-generated visual novels pale in comparison to one really well-made one. Do note that AI tools will most certainly ease the creation process of visual novels, as mentioned by @Tulip in their great post above. It's up to the team involved to make a truly great game.
In conclusion, I think there's some merit to using AI for parts of visual novel development. If you're on an extremely tight budget or prefer to do things yourself, then I think it's fine to use AI tools to get certain assets completed. Results can vary, but having a means to complete and share your story when you don't have the money otherwise is an admirable use of AI tools. It's good to use AI tools for:
Prototyping your work/Creating assets on a budget
Creating portfolio pieces
Game jams
Student work
However, if you're considering a large-scale commercial project, please consider saving your money and hiring other artists to help out. Consumers will also appreciate transparency when it comes to AI content. Consider adding a disclaimer explaining your usage of AI tools for your projects.