Whether light on dark or dark on light is better varies not just by person but by device and lighting conditions. I’ll take dark on light on an e-ink device every time. On LCD I usually prefer light on dark.
In general, I think it’s a travesty whenever users can’t select their font, font size, colors. Especially when it can make something entirely inaccessible to some people. I can imagine a game with elaborate typography and/or textual special effects where an accessible version would implicitly be an adaptation… but if such a game already exists, I haven’t seen it. I haven’t played any IF where I’d consider it to be a good trade-off to exclude people because your color choices are too precious to allow changing them.
I also know painfully well how hard it is to get people to care about digital accessibility issues when it’s literally part of their job, so it’s not going to be an easy sell for hobbyists giving away games for free to put more time and effort into it. So I hope that people writing IF development / game playing software will keep these issues in mind and default to allowing flexibility on these grounds. (Yeah, I know that those are often people giving away things for free, too.)