It isn't though, it is working as intended. You don't even need to do crazy things to get it, just 100 Enchanting. That said, I agree it makes the game too easy, and people can just not do it if they feel the same way. TES are not competitive games, making the game more enjoyable for yourself while someone else takes the easier path doesn't affect anything in your game.
Yep. "Just" 100 Enchanting.
Between raising your Enchanting up that high, and then deliberately making the items.... seems like getting "free" spells takes a good bit of effort. Definitely not something you'd just fall into accidentally. No-one's twisting your arm to do that.
Seems kind of like 100% Chameleon in Oblivion. Yeah, you can do it, if you put the effort in. Yeah, it's overpowered. Yeah, it's boring.
Easy solution - don't do it. I think I tried it once a looooong time ago, thought it was silly, and then never bothered trying again. Why do something that makes your game boring? Seems like a silly way to play.
(I've never played a mage yet, but I suspect that if I was - and had high Enchanting - I'd put a mix of enchantments on my gear. Maybe some extra Magicka, maybe some elemental resists, maybe a mix of mana reductions, so that I could cast several types of spells at a more reasonable cost, rather than one type for free.)