I wouldn't call it "spoiling the fun", half the fun of Elder Scrolls games is that you can become transcendent.
In Arena, you start humbly, but rise high enough that you destroy Jagar Tharn, one of the most powerful mages in the whole of the history of the Elder Scrolls games.
In Daggerfall, you're the right-hand man of the Emperor, and seek out a world-ending superweapon, and may just take it for yourself.
In Morrowind, you are a god, or very close to. The reincarnation of the Nevarine. That you can become overpowered makes sense. Bandits should fear you. Ordinary people should.
In Oblivion, you're the right-hand man of someone who ascends. You walk into literal Hell and fight demons. The bare mysteries of the world are laid clear by you. You steal the book of spells of immortal characters.
In Skyrim, you're descendant from a man who became a god. You have a gift that can shatter the heavens, and break open portals between worlds. You kill the son of Akatosh.
You're right, it is design, because it makes sense.
If anyone else here on HN is a fan of talking about what "makes sense" in the context of elder scrolls, I'm a big fan of /r/TESlore on reddit. Everything from explanations like the above, to how specific enemy groups became the way they were (e.g. the falmer in Skyrim), to theories of the economics underlying the games.
I think you might be confused with something like 'mysteries laid bare'. Bare doesn't mean foundational and if mysteries were already bare, what kind of mysteries would they be?
In Arena, you start humbly, but rise high enough that you destroy Jagar Tharn, one of the most powerful mages in the whole of the history of the Elder Scrolls games.
In Daggerfall, you're the right-hand man of the Emperor, and seek out a world-ending superweapon, and may just take it for yourself.
In Morrowind, you are a god, or very close to. The reincarnation of the Nevarine. That you can become overpowered makes sense. Bandits should fear you. Ordinary people should.
In Oblivion, you're the right-hand man of someone who ascends. You walk into literal Hell and fight demons. The bare mysteries of the world are laid clear by you. You steal the book of spells of immortal characters.
In Skyrim, you're descendant from a man who became a god. You have a gift that can shatter the heavens, and break open portals between worlds. You kill the son of Akatosh.
You're right, it is design, because it makes sense.