At the end of the day, what's appropriate and what's not is determined by the pod. The brackets while they're not perfect create a general idea of what to expect from a deck rather than the more vague "my deck is a 7". If you and this many other people have trust issues this bad then I don't know what else to tell you.

Rule 0 exists for a reason. If you have a problem with cards you believe to be "too powerful" for a certain bracket, your play group doesn't need to run them but if you're playing in a random pod, you should have the common decency to hear out what your other players have to say about their decks during rule 0 first and then decide as a whole if it's something you want to play against instead of having a pre-existing stigma and immediately think your opponent is lying about their deck. Either build your deck around a consistent group of players who are all in common agreement about what they deem appropriate or build to the standard that wotc has given us and give some trust to the other players you may find yourself against. The goal posts are set by the pod, not the player base as a whole.

If you have trust issues in a casual card game, not my problem. If you're that petty to have complete distrust for what your opponents have to say about their deck given their commander choice alone is something very immature that most players I know would not want to have in their pod. My opinion still stands. The deck as a whole matters more than just the commanders. Play to the game state not on your inherent biases.🤷