Mjolnir is just a hammer. Altars are just wood and stone. Runes are just an alphabet.

Left alone; any and all of these are just mundane and profane objects. They only achieve sacred status as we put our belief in them.

They CAN be sacred and they often are sacred, but they are not inherently sacred. Just like wine or meat or mead or anything else that we might use as an offering becomes sacred when we offer it to the gods or the wights.

Would you call mead sacred because Odin stole the mead of poetry I his pursuit of wisdom? No, that is foolish because your mead is not his mead.

But mead you might offer him will become sacred because it is being offered.

It isn't wrong to feel the Futhark runes (Younger or Elder) are sacred, for they may be sacred to you; just don't tell other people they must be sacred to them because they aren't.