The fact that iOS does not have support for generic storage devices has nothing to do with MFi. I do not understand why you think it does. It has everything to do with the fact that iOS simply never implemented support for them. Prior to the Files app existing it didn't make sense to support (because there would be no way to expose it), and Apple never added support after creating the Files app.

> i.e. as a storage accessory manufacturer, you need to add an MFI DRM chipset and pass MFI certification for Apple to allow a USB link with iOS.

How do you explain all of the previously-listed generic USB accessories working when plugged in via the Camera Adapter, given that they don't have MFi chips?

All of the "USB flash drives" you listed aren't using a USB connector, they're using a Lightning connector. The use of the Lightning connector is what requires MFi. In theory[1], a third-party app could implement support for an actual generic USB flash drive plugged in via the Camera Adapter. And if Apple implemented OS-level support for USB storage devices, overnight all generic USB storage devices would start working with the Camera Adapter, without any MFi chips.

> So - in conclusion, USB Mass storage - a feature widely available in mobile, and desktop computing since the dawn of the spec has been crippled by Apple on purpose to milk money

If the purpose was to extract MFi licensing fees, Apple would have implemented support for attached storage in either the OS or the Files app and simply required the MFi chip. That would have allowed a third-party ecosystem of attached storage for iOS to exist. But Apple hasn't done either of these things, and until your link, I literally had no idea anyone even bothered to make flash drives with lightning connectors (given that this requires the use of a custom third-party app to use). I'm actually quite curious what happens if you use the USB connector on one of those drives, plugged in via the Camera Adapter, with the relevant third-party app.

USB mass storage doesn't exist on iOS because, prior to the Files app existing, there was no exposed concept of a user-accessible filesystem and therefore no way to expose the USB mass storage to the user. Since the introduction of the Files app, it would be quite nice if Apple were to support USB mass storage as a location in Files, but it seems they never thought it was worth doing (probably in no small part due to the need for the Camera Adapter to even plug in a USB storage device; now that we have a USB-C iPad the argument is stronger for adding support to Files for this). This restriction is entirely a consequence of Apple's reluctance to have a user-visible filesystem and not related to the MFi program.

[1] I say "in theory" because I don't actually know if the appropriate APIs for talking to generic USB devices plugged in via the Camera Adapter are available for use by third parties. I'm not sure what those APIs would be (having never implemented a USB driver myself) so I don't know what to search for. It is of course possible that Apple has restricted the ability for third-party apps to talk to arbitrary non-OS-supported accessories to the MFi program, but the ability for third-party apps to implement support for arbitrary accessories isn't really the point of contention here.