In a world where there is 200 year old salisbury steak and pork and beans still waiting to be eaten in every other broken refrigerator,
Well you can blame Bethesda for that, FO1-2 did not had any consumable pre-war food (there were a few items but non-consumable).
And even FO:NV makes a joke about who would eat 200 year old food.
lights working in most every building in spite of all the power lines hanging limply and broken from their poles,
Pay a closer attention in NV, you have jury rigged generators being used and some installations would have backup power generators.
I do say this, you are right if we discount land lines but NV did attempted to show WERE the power was coming from as FO3 did not.
and running water in every broken sink (but not bathtubs! they're all broken) in the wastes,
And yet another Fallout 3 issue, New Vegas show things as the NCR had build a water pipe to supply certain areas, the only place with extensive utilities is New Vegas as the others are small local towns were its inhabitants could very well maintain their utilities as they are self-sustaining and not connected to a main grid were repair would be difficult if not downright impossible.
I'm not going to quibble about where a faction gets it's combat armor (or Roman centurion costumes).
Things do not exist in a void, the Legion having a endless supply of Combat Armor would make no sense, in fact it would be
ridiculous when we discount "video game logic" (that is none).
The fact you list what are illogical aspects of the game and then say "its ok to have ANOTHER illogical one because we have them" is not much of a argument, you shown no reason to WHY should the Legion go around in Combat Armor besides "we have a lot of things that do not make sense so lets add another".
Also as I had to bring up Fallout 3 I also going to point out the only ones that used Combat Armor in Fallout 3 were the Talon Company, Reilly's Rangers, Rivet City Security and Tenpenny Security showing its not commonly available enough to be used as basic armor.
Edit:
Fiends use one of most powerful energy weapons in the game.
Yes, they can use energy weapons but look were they are housed.
Where does everyone take weapons and armor in post-apocalyptic world?
Some are now manufactured.
Heard of the Gun Runners? also the BoS have limited manufacturing abilities.
Caeser can find in Arizona good amount of combat armor to equp with veterans. He can paint red bulls and good armor is made.And he can equip them with simple shot guns or any other type of fire power.
Let me see Legion Centurion armor entry ...
* The Helmet is that of a super mutant brute's, polished and with an added centurion's frill
* The right pauldron and the right forearm are pieces of T-45d Power Armor. Coincidentally, the NCR salvaged T-45d power armor are missing their shoulder parts.
* The left forearm and gloves is a piece of the Leather armor.
* The chest piece appears to come from the same source as that on a Super Mutant armor.
* The part of both legs is a piece of the Raider blastmaster armor.
* The piece worn at the hips is from the NCR Ranger patrol armor.
* The boots appear to have been taken from Combat Armor.
Their DT is 18, Ranger Patrol Armor is 15 (Ranger armor does have more HP, 500 vs 450 and weights less)
So ... why would Caesar order the issuing of Combat Armor that have the DT of 15, HP of 400 and weight of 25? the only aspect were its superior is it weight less.
Oh and armor HE CANNOT REPLACE!
Also before you bring up that is Legion Veteran Armor I should be talking about, I point out Combat Armor is Medium Armor, the Legion have the best Light Armor in the game with only the Vault 34 security armor standing out (as its the best Light Armor if we discount the Gladiator Armor that we have to since its quest related), the NCR Armor is all Medium (with the exception of the Salvaged Power Armor) and if you look at the NCR Bandoleer Armor that is their basic armor its worst that Combat Armor and yet its NOT their basic armor.
If you want to argue about the Legion using Combat Armor I can make THE EXACT SAME ARGUMENT about the NCR since both apply and the also the reasons to why they DONT use it.
Brotherhood loses against NCR becuase of its numbers not dependant on energy weapons. It actually gives them an edge.
I said attrition, the Brotherhood cannot withstand long conflicts because they can neither replace their personal or their equipment as their enemies (in this case, the NCR) can, even if personal losses were unsuitable the fact is eventually all their fancy equipment will break beyond repair.