they want to go by the rules of Commander and push the format as far as they can
The rules of Commander in as far as they're 100-card singleton with a command zone feature, yeah. However, I think most cEDH players would rather have Flash in the format than Protean Hulk, and yet they have to abide by that ruling for whatever arbitrary reason. Simply-put, the reason that cEDH isn't a de jure separate format is that there isn't an anointed authority on it.
The point of creating two separate banlists and thus two separate formats (legacy-vintage) is not to dissuade all competitive play in the one, but rather to change its nature. The main issue with fast mana is that if you can afford the cards (or you just proxy them because you're not retarded), you put them in every single deck because they will allow you to put a lock on the game before the average player can actually respond. By splitting that play pattern off into a distinct format, you instead create one where you can reasonably expect that people will have the ability to respond to your shenanigans if they've played 'normally' and are packing interaction, rather than one where the game ends on turn 3.
It also means that you can assume people will have a way to deal with certain cards that, frankly, wouldn't be an issue if people weren't at-large retarded. There'd be no reason to ban Sylvan Primordial in cEDH, much less even Gifts Ungiven, because you can expect that players in that format have opted-in and will adapt to those cards, rather than in normal EDH where players will side out swords so they can put in another 6/6 trample for 6.
This is an issue where the RC sitting around doing fuckall really comes in to play. Because there's basically no resources out there to determine deck power level, and of what is, they're not really agreed-upon and propagated properly. In a world where the RC actually did something, they would both clarify and codify the different power-levels and curate a list of all the cards that qualify as 'high.'
I personally find the numerical system doesn't fucking work, and low-mid-high is a lot better. The way Canadian highlander attaches points-values to cards is interesting, but I ultimately find it a bit flawed because of how synergy works: intruder alarm is broken in Kumena, but worthless in Hakbal, for example.
"I am gonna play a Mill Deck and put in zero graveyard hate and then cry about power level when someone casts Eerie Ultimatum"
Things like this being so common is also why I don't buy a lot of people's excuses of "you can't make these formats more complicated, how will people ever learn?" People can somehow be expected to look up a mill list and shell out for it, and they do - and yet they don't understand the use of graveyard hate?
People are so willing to do research into building a deck that they do so before they understand basic functions of the game itself, and are in this state expected to assign a number to their deck... yet they can't be trusted to comprehend two separate banlists? Or the notion of Banned-as-Commander? It all boils down to the RC not wanting to do anything, because if they do, people will shit themselves.
why? Because it has bad gameplay, You either dogpile the Tergrid player or the Tergrid player eventually casts Dark Deal and gets everyone's hand
Tergrid is a great example of something that is probably fine in CEDH (in so far as it's irrelevant and slow) but something no one wants to play against because you have to keep their commander removed or remove the player.
This is also why combo fundamentally just does not work with the casual format, lol. The correct play pattern is always to pressure and kill the combo player outright, since at any point they can pop off and win. It's a game state that doesn't exist in 1v1, since there you're necessarily always pressuring them.
In cEDH, the expectation is that everyone is either doing that, playing something like Winota that has light stax to back up a fast aggro strategy, or playing a midrange pile that generates insurmountable advantage to totally neuter combo, and so it fits in to that play-pattern nicely. But in casual, the combo player always whines and cries when you correctly prioritize them, and without fail every time you knock them out (because they have no removal or board presence), they go "if I just got one more turn, I'd have won the game, why do you target me all the time"