

I wish to advocate in the name of DIY minimalism. That is to say, it’s true that none of us – Linus Torvalds is not in the room, right? – can hope to churn out anything approaching a full-blown filesystem on the order of ext4 or NTFS if we worked our entire lives. But if those filesystems were the end-all-be-all of innovation in those spaces, the richness and intrigue of computer science would have died out long ago, relegated to only the pinnacle of engineers and no one else.
But I feel like that can’t quite be the case, because all engineering is about achieving careful balances. And as fine as ext4 is, it must be said that it’s anything but minimal. It’s full-featured, which also implies that it might have more than what any one person requires. If OP wants to write a very compact filesystem designed for 8-bit microprocessors, I can’t badger them with ext4’s existence, because that’s not going to be usable on an 8 bit machine.
Much like how Python includes a really tiny HTTP server, and we can all agree that it’s orders of magnitude less sophisticated than nginx, such implementations can have their time in the sun. And I think a tiny, absurdly minimal, almost code-golf of a filesystem, might have a place in this world, if OP really wants to undertake that effort.
Computer science, I wish to believe, still has doors awaiting exploration.
I vaguely recall what was effectively a delay-line implemented using terrahertz-modulated lasers aimed at the retro reflector on the moon from Earth’s surface. The data storage capacity was something in either the hundreds of GBs or low TBs. But I can’t find the reference.