Fascinating. How does one go about writing one of these in 2021? Do analogs to Unity/Unreal Engine exist for interactive fiction, or are people rolling their own?
Inform 6/7 is the most popular of the parser-based languages, with v6 being closer to a traditional programming language and v7 being a fascinating, natural-language based programming language that is powerful but can be difficult for those steeped in traditional programming languages to wrap their head around.
Twine is the most popular choice-based system, supporting three languages that range from basically Javascript to no-code.
Honorable mention to both 1) Ink which is my personal favorite choice-based IF language and integrates well with Unity but doesn't have a great default presentation and 2) ChoiceScript, which is frustratingly limited (by design) but supports an incredible ecosystem of pro, semi-pro and amateur game writers (at ChoiceOfGames.com).
Ink is amazing: it's modular and is getting close to modern programming languages in terms of tooling. AFAIK all the others are still distributed as monolithic applications.
Ink has an IDE that exports to web, but there are also libraries for C# and JS that can be embedded in other programs, a Unity plugin and a VSCode language server.
Writing your own is, of course, an option, but don't underestimate the task. A "simple" POC is usually very easy (my son and I did one in an afternoon). But building an engine with block-able exists, recursive containment, item interaction (eg. "turn bolt with wrench" and the custom functions they need), can be a much larger effort.
