what you say is literally impossible in Oblivion.
Impossible? I'm sorry but this is absurd.
Oblivion requires sound files, yes. What does the presence (or absence) of sound files have to do with constructing imaginative quests that go beyond Fed-Ex or hack-n-slash? You can't seriously be claiming that we are all stuck with hack and slash because the game is voiced? The Lost Spires could have done many things that went beyond conventional quests.
Why should he have realized it wasn't hack-n-slash? He wouldn't have found that information in the mod's readme. The readme tells us we're able to join an archeology guild. Is it so very surprising that some players might expect quests that give the player the feeling he's engaged in archeology? The mod could have, for instance, offered the player the chance to find and collect bones, clean a dig, interview archeology experts around Cyrodiil, turn in reports, et cetera, with XP awarded for completing these tasks.
Oblivion is 5% of RPG, and 95% of hack & slash. There's little that can be done about it...even modders.
In fact, there are quite a few non-combat-oriented mods out there, and many more being worked on. Et In Arkay Ego, Integration: The Stranded Light, Gweden Brothel and Shadowcrest Vineyard are just four mods I can think of off the top of my head that either contain no hack and slash at all, or almost none. There are many more.
Much can be done about it.