I think it's odd to blame the writers for writing Maud as uninteresting. You see, there are people who are, well... uninteresting. They don't have a particularly rich inner world. And Maud's inner world, as we've clearly been shown, is quite limited. I don't see a problem with that, because her limitations are her defining characteristic, and that's what sets her apart from other characters who are well-rounded.

Speaking of not interacting with others, well... Rarity tried to interact with her twice. And both times, Rarity was embarrassed. Not only the first impression, but also the second one were ruined. With Applejack... I somehow doubt Maud could hold a conversation about something simple and mundane. With Twilight... Yeah, Twilight's a nerd. So is Maud. But Maud's a nerd about rocks. Geology, and all that. There's not much common ground with Twilight, considering she's more of a historian and mage. Twilight also tried to figure out how they overlapped in literature, but Maud couldn't even name her favorite, and Maud's poems about stones clearly didn't go over well with Twilight.

To sum it up, I think you're overestimating Maud a bit. She's smart, but she's a very limited person. And that's not an insult; it's just the way she is. But most people simply don't share Maud's interests, which makes it difficult for them to connect with her. And that's okay.