Beyond AirDrop which only works between like devices, how else can files on an iPhone be transferred to another device without iTunes, and without using a 3rd party? I'm not being adversarial, I really want to know.

I’m a little confused, you don’t want to use 3rd party apps (like a Microsoft app to interact with nearby MS stuff) AND you don’t want to use Apple 1st party apps?

It sounds like the only thing that would’ve satisfied you would’ve been for iOS to natively understand whatever the Microsoft system is for broadcasting videos? I agree it would be delightful if Apple and Microsoft could agree on a “I’m a short term drop-point” “send to any nearby open drop-point” API, but the absence of this doesn’t seem likely to be either Microsoft’s or Apple’s fault.

The Apple way to do this would’ve been to send an iCloud email. Apple Mail would’ve uploaded the file to a server, and a short-lived link would’ve been created, to avoid SMTP size limits.

Pretty much exactly what you ended up doing but manually via Firefox Send.

I don't understand your confusion. What I would like to see is the iPhone to support the use of its native Bluetooth radio to connect to another device with a Bluetooth radio and implement the native Bluetooth file transfer protocol. Why would I want to use a 3rd party app/program which incurs a data charge to download, and possibly an account setup which means information leakage.

> The Apple way to do this would’ve been to send an iCloud email

Since iOS 12 they also have a "copy iCloud link" share option that gives you a Dropbox-style file download page.