I believe the main issue is not so much that everything requires Aluminium (since it IS in fact very abundant "In the Earth's crust, aluminium is the most abundant (8.3% by weight) metallic element and the third most abundant of all elements (after oxygen and silicon)." ) , but rather that nothing requires Oil anymore , unless you plan (and can, not sure how obsoletion works now) on building WW2 era units in the Modern era (which i hope is not the case as it would be dreadfully anachronistic ).
I think what they should do is allow some of the units to still require Oil, perhaps even going as far as needing both oil AND aluminium to build some of them (like, Modern Armour or Jet Fighters etc).
I just don't like the "disappearance" of oil in the modern era (as a requirement at least), seeing as we are still very much dependant on it today.