[...] Or so on and so forth, which is already a terrible UX worthy of criticism.
I mean... You get what you get with the provided infrastructure. If you want decentralized storage, this is what you get. I think it's a good thing. The UX is fine from my perspective. I'm not using WhatsApp for sensitive data or conversations that I need to save indefinitely. So for that purpose, it's good enough, UX wise. I use the web app all the time, too.
It’s not stored on any server
It is stored as an encrypted blob on your gdrive. It asks you about it on every login. Otherwise, how would you recover your chat history if you lost or changed your phone.
That's different. That's not what I mean by your messages being "stored on a server". What you're talking about is an incremental backup sync. It's not where messages are fetched when you receive messages while chatting. Not to mention it's entirely optional last time I checked. I have it disabled and it doesn't nag me about it. 🤷♂️
The whole security aspect is surely an issue regardless of app, if the perpetrator is looking to steal your data rather than your hardware. If they have your phone, and bypass the lock screen, then they have your 2FA app and everything. You're fucked regardless of app.