Looks like a lot of the stuff was already touched upon but here's my thoughts.
For an example, Tesla SuperChargers can only be used with Telsa. But if another car is designed to use such, Elon musk said they would be open to other brands of EV's. But so far, nobody has designed a car to use them other than Tesla.
It can be more tricky than you expect. For an example, notice there is not even a single button on a Telsa Charge Station (other than the one on the handle that will open a Telsa charge door via wireless) . No way to make a payment or anything. When I plug in, it reads my VIN number and sends a charge to my Tesla account. So all I do is plug in and walk away. Almost too easy.
This doesn't apply to Rivian, they haven't disclosed how/if they'll plan to open their DCFC network. Setting up payment methods without app/credit already works outside Tesla. The Mach-E can plug into Electrify America chargers, and they pay through an account handled through Ford.
And DC voltages have to be in the program for different makes of vehicles. Battery voltages and such can be a lot different.
All CCS charging-capable vehicles adhere to the standards in which they can accept at least the minimum voltage set. Even Tesla's propriatary superchargers have this feature.
Too many variables with charging with DC when away from a "standard" such as CCS (which Tesla cannot even use). The only real standard is J-1772, Can't find an EV that cannot use J-1772.
But on DC, we have a lot of different standards and that may never change. So we have CCS, CHAdeMO, Telsa Super chargers, Rivian and perhaps even more. But all of those vehicles can use J-1772 AC charging in one way or another.
While Tesla's Supercharger can be considered a standard, it still uses the CCS requirements. There's already CCS1 adapters made in Korea which work on Model S/X. There's no fancy equipment necessary to convert the form factor.
Another standard you can add to that list is China GB/T which is a lot like CHAdeMO but I believe the latest version marries the two together.
The real charging standard "war" is ccs1/2 vs CHAdeMO. I think it might just settle on those two standards indefinitely between east and west. It'll definitely get tricky in 25+ years when we import classic cars. Hopefully, we can hire techs who can convert older EVs to other charging standards.