"Yet" is key. You can't say the RPi is the most open platform if it's predicated on some future condition.
That said, I shouldn't be so critical. The state of free graphics drivers on ARM SBCs is pretty abysmal and any improvement is a good thing. Mostly I object to the assertion "RPi is a free and open platform," but rereading your original post you didn't actually say that. Perhaps we should say "RPi is one of the least-closed platforms." It will be great to see the FOSS VC4 drivers mainlined into the Linux kernel.
Survey of FOSS ARM graphics drivers https://www.phoronix.com/scan.php?page=news_item&px=MTQ3MTM
Hardware that can run the Lima free graphics driver: https://limadriver.org/Hardware/
Hardware that can use the Etnaviv free graphics driver: https://github.com/etnaviv/etna_viv#socs-with-vivante-gpu
That's over 5x the price for the cheapest model (iMX6 OpenRex SBC Basic, €199 in quantity 1, http://www.voipac.com/#category3 ), at that price you'd be better off getting an x86 board.
> "Unfortunately, the current end result seems to be a Linux that doesn't even have support for USB or ethernet."
You forgot a word at the end of that statement... " yet". Furthermore, expensive outliers like the OpenRex aside, it's still currently more open than its main competition.