I also wrote a KV system to keep track of metadata (tags) for an object store I invented. I discovered that it could also be used to create relational tables and perform fast queries against them without needing separate indexes.
I started calling it a database and many people complained that I was misusing the term because it can't yet do everything that Postgres, MySQL, or SQLite can do.
Databases have a long history that reaches back much further than the modern, full featured SQL databases we have today. What you built sounds like it would fit in well amongst the non-sql databases of the world, like Berkeleydb, indexeddb, mongo, redis, and so on.
Git is also a database. I got into this argument with someone when I proposed using Github as a database to store configuration entries. Our requirements included needing the ability to review changes before they went live, and the ability to easily undo changes to the config. If your requirements for a DB include those two things, Github is a damn good database platform! (Azure even has built in support for storing configurations in Github!)