Aha! You know I totally had that exact phrase in my reply, right after my sense of humour line, and then I edited it out before I posted because I second-guessed myself. 
Great minds think alike and all that though.
I’m sorry that it was your mother that said that.
You don’t need to be Mark Twain. You’re writing a game that a lot of people are enjoying. You make great posts on the forum. Can Mark Twain say that? (Well no, since he’s dead and all).
Were you trying to be Mark Twain? I’m serious.
All that critique says is that the critic was comparing you to Mark Twain and didn’t find you to be a copycat/clone. So that’s what that critic was looking for in your writing. It’s only relevant to your writing if you were trying to write like Mark Twain.
Critique can often say more about the critic than it does about the one or work critiqued. For instance, if you hand me something, I’m going to have an easier time pointing out “That should be blonde, not blond, unless you were aiming for US English.” I am not the person to hand a typo-ridden first draft, and because I essentially will be unable to see the story beneath the technical errors.
What is the goal of writing? To connect/resonate with your target audience. If you’re reaching your target audience, you’ll get good reviews, or at least a good balance of good vs. bad. If you’re getting more bad reviews, then something’s keeping you from reaching your target audience.
I had an incident like that, myself, with one of my short stories, where I was getting all bad reviews from confused readers. This particular story had nearly been published in target genre 'zines multiple times, so I knew it was good—but I realized the cover didn’t quite nail the genre. I adjusted the cover to blatantly signal there was a sci-fi aspect, and now the target audience can find it.
[sighs] Historically and colloquially, they is singular as well as plural. It was only more recently (linquistically speaking) that the academics assigned it as plural and called it wrong for singular. [grumbles]
My mother sniped at me to “write something meaningful”, my father told me that a young girl couldn’t possibly write meaningful fantasy (ETA: I was somewhere around 20 at the time), and my brother scolded me because some poems I wrote were “wrong” because they didn’t have his side of the story—and the main one he protested wasn’t even about him, and the one that was actually about him was still completely true after he gave his side of the story.
[twiddles thumbs] In my case, that was only the tip of the iceberg in how I was treated, but it’s now only “was” because I’m now hundreds of miles away and they don’t know where I am.
I’m not saying that your family is that bad—just that you’re not alone in family making hurtful comments.