Nice idea, but consent a question: this web-app do home inventory, and home inventory only, another do bank transactions record and stocks and them only, another is only a webmail + webcalendar, ... ALL not integrated not easy to integrate despite with classic modern poor man's solution (many WebVM tabs open and cut&paste) witch is the very same limitation of classic modern desktop applications.
In the past, a far past, such limitations, walls, walled gardens, have not existed. An operating system in the past was a single application, with a "common layer" witch is what we can call base system + base userland and countless of variations any users, yes users, not developers, can made.
How many here think it's about time to came back to such model? Modern applications both desktop GUIs and WebUIs are like they are for commercial purpose, not by nature, Plan 9 GUIs, Xerox GUIs, LispM GUIs in different time in history were NOT like that.
Personally I try to re-create such classic desktop in Emacs and it's does work, even if in a spaghetti manner, for instance my "agenda" is not really a dedicated app (it's org-agenda, but for me it's just a collection of notes with scheduled/deadlines/todos in them + various catchall), so mails are not used via a dedicated UI isolated from the rest (I use notmuch, but accessing mails via org-mode links, like notmuch-search:tag:unread, so mails are linked in relevant notes, and those notes (org-mode/org-roam managed/accessed) "link" attachments, comprehend inventory, transactions, mails, metadata, ... all integrated and filtered in various way (plain search&narrow like org-roam-node-find, org-ql queries, ...).
Long story short: who do not know what I describe in the above paragraph, didn't you feel the missing integration in modern tools? For those who know instead: why we keep even in FLOSS land such modern/archaic model?