Microsoft made an attempt back in 2003 at creating a "smarter" file system with rich metadata based on a real database engine (MS SQL Server) ... but eventually abandoned the project: https://en.wikipedia.org/wiki/WinFS
WinFS wasn't necessarily going to completely replace NTFS but Microsoft did have ambitious plans for its integration into everything.
It's interesting that other platforms like Unix/Linux/Apple that were designing "next generation" file systems like ZFS/ext4/APFS after the failed WinFS project had a chance to try adding their own WinFS smart metadata features to but they didn't.
The later fragmentation of user data being spread around in the cloud such as AWS objects, Apple iCloud, Backblaze backups, etc instead of every file saved on home computers makes a "universal rich metadata index stored in a database engine" to be a cross-platform standard by all operating systems less realistic today than back in 2003. Therefore, the core os file systems remain a "dumb blob of bytes" with a separate layer of metadata index db in vendor-specific schemes like Apple Spotlight db, Windows Search in ".edb" file, etc.
All I want is dumb files with something like SQLite replacing or augmenting the allocation table. Then sprinkle on some new capabilities incrementally.
The 'file table' contains a 64 byte record for each object and has some very unique characteristics that make searches incredibly fast (e.g. it can find all the photos in under a second, even if there are 20 million of them among 200 million files). You can also attach various metadata 'tags' to each object and find matching objects based on them.
The project is in open beta and anyone can download it and try it out on their own computer.
It has relational database-like semantics for metadata.
I can search millions of records in a split second in SQL. But searching records on my hard disk takes enormously more time. The solutions out there for speeding it up (like Windows Indexing service) rely on asynchronous indexing that's patched on top of the filesystem instead of integrated realtime within it, and are subsequently brittle (in my experience), slow down your computer at inconvenient times, and too often aren't instantly up date.
Being able to have stored procedures execute when changes trigger would be another interesting aspect that could take the place of event filters and file watchers (especially if critical portions could be configured to happen sequentially & atomically, akin to IRQ handlers).
I feel like databases have gotten lots of love over the decades and are super optimized (and by this point are pretty dang reliable). Filesystems feel like they lost their time in the spotlight and have floundered with less innovation.
Hardware that calculates CRC's of blocks in realtime would also be awesome (imagine what it would do for sync). The ironic thing is your HDD already does this, there's just no way to tap into that information at the software / filesystem driver level.