Drag and drop, text inputs, selections, UI elements, keyboard shortcuts, state preservation – none of those worked as they should. I would accept a divergence for a legitimate improvement, but it's just system-wide basic functionality missing.

All of that works correctly in Telegram. There is great value in adhering to the system conventions, design, and using native elements – it's fairly clear what is supposed to be what, a good chunk of the time, and there is minimal context switching as I use other native apps.

Those are services.. where would people go to replace Instagram? Twitter? Airbnb, what other big service has brand mindshare that people know about for fly-by-night unregulated sleeping accomodations?

I don't think iOS/Android design would cause them to lose or gain users.

Uber and Slack look nice but they're rather slow. After a week, the "looks nice" part ceases to matter and all that's left is the annoyance of waiting 200ms-1000ms between every action.