Mage hand can't throw a lever by design so that's not a bug,
I still think it’s a valid thing to complain about, though, even if Larian have purposefully made their version of Mage Hand this useless. As far as I’m able to tell, as long as the caster has line of sight to a lever, per 5e a Mage Hand should be able to pull it.
As per Niara’s
focused spells feedback, the mage hand implementation in the game is very poor.