I think anybody who really thinks about it would have to agree modern OSes are a disgusting mess.
-- Why does an 8 core mac have moments that it is so busy I can't even click anything but only see a pinwheel? It's not the hardware. No app should have the capability, even if it tried, to slow down the OS/UI (without root access).
-- Yes, it should be a database design, with permissions.
-- Yes, by making it a database design, all applications get the ability to share their content (i.e. make files) in a performant searchable way.
-- Yes, permissions is a huge issue. If every app were confined to a single directory (docker-like) then backing up an app, deleting an app, terminating an app would be a million times easier. Our OSes will never be secure until they're rebuilt from the ground up. [Right now windows lets apps store garbage in the 'registry' and linux stores your apps data strewn throughout /var/etc, /var/log, /app/init, .... These should all be materialized views [i.e. sym-links])
-- Mac Finder is cancer. If the OS were modularizable it'd be trivial for me, a software engineer, to drop-in a replacement (like you can with car parts).
-- By having an event-driven architecture, this gives me exact tracking on when events happened. I'd like a full record of every time a certain file changes, if file changes can't happen without an event, and all events are indexed in the DB, then I have perfect auditability.
-- I could also assign permission events (throttle browser CPU to 20% max, pipe all audio from spotify to removeAds.exe, pipe all UI notifications from javaUpdater to /dev/null)
I understand the "Well who's gonna use it?" question, but it's circular reasoning. "Let's not get excited about this, because nobody will use it, because it won't catch on, because nobody got excited about it." If you get an industry giant behind it (Linus, Google, Carmack) you can absolutely reinvent a better wheel (e.g. GIT, chrome) and displace a huge marketshare in months.