Thanks for the reply; Train had a couple good follow-ups, so I only wanted to reply to this bit (emphasis mine).
At a sufficiently high power level and fixing density, it's simply not possible to find mono-color cards "just as powerful" as the gold cards. Young Pyromancer and Dark Confidant are maybe their colors' best 2-drops, but they're no
Kroxa. Oblivion Ring is good, but it's no
Prismatic Ending or
Leyline Binding.
Tarmogoyf might be better than
Territorial Kavu, but the Kavu trumps all the other mono-
2-drops.
But that doesn't mean that drafts devolve into straightforward "pick the best card" decisions, or that all the decks turn into 5-color nonsense. Even in a format with 3 cycles each of ABUR/fetchlands, you can't cast Uro and Kroxa in the same deck, and you have to draft and deckbuild around your lands as much as your spells. (Like I said earlier, in my opinion, that's a good thing, because it forces the FIRE-era nonsense to require some investment, even when there's not any risk in the cards' rules text.)
In other words, I have drafted my cube with heavy gold/fixing for 2+ years now, and I simply have not experienced the drawbacks you warn against. Indeed, heavy gold/fixing is
more suited to my Cube design goals and my personal definition of fun than the intense mono-color paradigm I began my cube with. (I believe Train and blacksmithy also enjoy similar fixing paradigms, if they won't mind me speaking for them.)
in conclusion - most cube advice boils down to "make your cube more like mine" and, despite my best intentions, this has been no exception