Cardpool is not the basis of the MtG comparison, but gameplay is.
Give me a 56 card pool of MtG and a game of Magic any day. I have Academy, and whilst I'm certainly not it's target, I don't think it's target meaningfully exists:
1) For those wanting a quick 30 min game, there isn't enough game there , and so many CCG's do it better, and yes MtG is the most obvious and accessible comparison.
2) For those wanting an introductory step into Arena, this is too small a step IMO for anyone that will actually get there. They will probably still need to move through Apprentice if they need babysteps, and even apprentice only has limited use - after the first time I taught using it, I have taught everyone else with full Arena and preset books, and had no problems whatsoever. The people who have problems are probably not the sort of players that will get big into the game.
3) For those wanting a dose of MW awesomeness, there is no substitute for full arena. It's the right game for some, the wrong for others, but cut-down versions just don't work.
Academy's only reason to exist is as an Arena expansion, and it mostly does that on the back of 3 cards justifying it's existence.