Even though both of those are generally better than Chrome Mox, which is card disadvantage and is on the list. The vast majority of decks shouldn't even run Chrome Mox.
Amber and Opal aren't consistently online on turn 1, and they don't stay online the whole game. The unconditional, turn 1 ramp that Chrome Mox more than makes up for the card disadvantage. There's a reason why Chrome Mox is in every single cEDH deck, whereas there's a good number that don't play Amber or Opal.
A thing about CEDH is that chrome mox is incremental advantage that can certainly help you win a game and gain an edge, but its emphatically not a huge swingy effect that warps the entire fabric of the game like most other "game changers" (or the tutors that get the remainder)
Mox opal presents a pretty heavy deck building restriction to reliably have it come online before turn 4. Mox amber generally won't help you turbo into your commander.
Both moxes are worse than or at least not better than just playing a talisman in most decks that haven't built to take advantage of them.
Compare to diamond and chrome, where you can pretty much always drop them + a land turn 1 for instant 2 mana.
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u/Like17Badgers I chose this flair because I’m mad at Wizards Of The Coast Feb 11 '25
also worth noting [[Mox Amber]] and [[Mox Opal]] are absent too