Design Dilemmas

I'll tell you about some design issues and the process of working through them, even though I can't actually tell you any of the details. Sorry about that, but you'll still get the gist.
One of many things I've been working on is a new card game, to be released in about 100 years. It's "somewhat similar to Magic: The Gathering." I have One Big Idea for what makes it new and different, and I've played the prototype a fair amount. It's fun. I've played probably dozens of my own prototypes, and having them actually be fun is a kind of rare and great thing, so that's a strong signal to keep going.
I discussed this game with several other professional game designers, some of whom actually worked on the real Magic: The Gathering. The problem, I said, is that even though it has the One Big Idea that makes it play a lot differently, it still is just too close to MTG. Like how do I not have a card that destroys a "creature," or that deals 2 damage to a creature, or Llanowar Elves, etc, etc. Even cards like Ball Lighting are hard not to have.
In my prototype, many specific cards are like MTG cards. Even though I think that's good for the game, I think the audience has a strong, almost irrational love of the "new" and would actually prefer a game to be new and different than for to be the best it can be if that means a lot isn't new. Every single designer I talked to including the MTG guy said don't be afraid to copy MTG. They said the more you copy it the better, probably, because it's damn good (I agree it's damn good) and that my One Big Thing and my completely different business model are more than enough to make it stand apart. They said of course many of the staple cards should be in the game, and not to avoid a bunch of good ideas just because they are in MTG.
Well, I didn't really listen. I think those designers are underestimating